Definition of dose rate for FLASH pencil‐beam scanning proton therapy: A comparative study

Deffet, Sylvain; Hamaide, Valentin; Sterpin, Edmond

doi:10.1002/mp.16607

Cited by 2 publications

(4 citation statements)

References 23 publications

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“…The prescribed dose was 67.5 Gy in 4.5 Gy fractions. Plans were created for a ProBeam system delivering 245 MeV protons with 165 nA beam current, setting a minimum spot time of 0.5 ms. Average dose-rates R ave in 5-field plans exceeded 40 Gy s -1 in ~80–95% of the volumes of oesophagus, stomach, kidneys, chest, heart wall and liver excluding GTV that received the prescribed dose or greater ( 25 , 26 ).…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

“…Several measures have been proposed to describe effective FLASH dose-rates for these irregular pulsatile deliveries. The simplest is the average dose-rate R ave ( 26 ), defined as the total dose-per-fraction D tot delivered to a tissue element, divided by the interval T between the first and last times at which the element is irradiated during the fraction. Alternatively, the pencil beam scanning dose-rate R PBS ( 24 ) excludes dose contributions below a small threshold

at the beginning and end of irradiation of the tissue element, thus…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

“…The percentile dose-rate R Perc is a variant of R PBS that defines D th as a fraction of D tot ( 26 ). Another variant is the maximum percentile dose-rate R MP , which represents the fastest rate at which a dose

is delivered to the tissue element.…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

“…Another variant is the maximum percentile dose-rate R MP , which represents the fastest rate at which a dose

is delivered to the tissue element. This allows for the possibility, for example, that the interval between delivery of cumulative doses of

and

might be shorter than the interval between delivery of

and

( 26 ).…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

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Navigating the straits: realizing the potential of proton FLASH through physics advances and further pre-clinical characterization

Fenwick,

Mayhew,

Jolly

et al. 2024

Front. Oncol.

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Ultra-high dose-rate ‘FLASH’ radiotherapy may be a pivotal step forward for cancer treatment, widening the therapeutic window between radiation tumour killing and damage to neighbouring normal tissues. The extent of normal tissue sparing reported in pre-clinical FLASH studies typically corresponds to an increase in isotoxic dose-levels of 5–20%, though gains are larger at higher doses. Conditions currently thought necessary for FLASH normal tissue sparing are a dose-rate ≥40 Gy s-1, dose-per-fraction ≥5–10 Gy and irradiation duration ≤0.2–0.5 s. Cyclotron proton accelerators are the first clinical systems to be adapted to irradiate deep-seated tumours at FLASH dose-rates, but even using these machines it is challenging to meet the FLASH conditions. In this review we describe the challenges for delivering FLASH proton beam therapy, the compromises that ensue if these challenges are not addressed, and resulting dosimetric losses. Some of these losses are on the same scale as the gains from FLASH found pre-clinically. We therefore conclude that for FLASH to succeed clinically the challenges must be systematically overcome rather than accommodated, and we survey physical and pre-clinical routes for achieving this.

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Section: Challenges For Proton Flashmentioning

confidence: 99%

at the beginning and end of irradiation of the tissue element, thus…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

is delivered to the tissue element.…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

“…Another variant is the maximum percentile dose-rate R MP , which represents the fastest rate at which a dose

is delivered to the tissue element. This allows for the possibility, for example, that the interval between delivery of cumulative doses of

and

might be shorter than the interval between delivery of

and

( 26 ).…”

Section: Challenges For Proton Flashmentioning

confidence: 99%

See 2 more Smart Citations

Navigating the straits: realizing the potential of proton FLASH through physics advances and further pre-clinical characterization

Fenwick,

Mayhew,

Jolly

et al. 2024

Front. Oncol.

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Time structures of proton pencil beam scanning delivery on a microsecond scale measured with a pixelated semiconductor detector Timepix3

Shen,

Ding,

Charyyev

et al. 2024

J Applied Clin Med Phys

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PurposeThe time structures of proton spot delivery in proton pencil beam scanning (PBS) radiation therapy are essential in many clinical applications. This study aims to characterize the time structures of proton PBS delivered by both synchrotron and synchrocyclotron accelerators using a non‐invasive technique based on scattered particle tracking.MethodsA pixelated semiconductor detector, AdvaPIX‐Timepix3, with a temporal resolution of 1.56 ns, was employed to measure time of arrival of secondary particles generated by a proton beam. The detector was placed laterally to the high‐flux area of the beam in order to allow for single particle detection and not interfere with the treatment. The detector recorded counts of radiation events, their deposited energy and the timestamp associated with the single events. Individual recorded events and their temporal characteristics were used to analyze beam time structures, including energy layer switch time, magnet switch time, spot switch time, and the scanning speeds in the x and y directions. All the measurements were repeated 30 times on three dates, reducing statistical uncertainty.ResultsThe uncertainty of the measured energy layer switch times, magnet switch time, and the spot switch time were all within 1% of average values. The scanning speeds uncertainties were within 1.5% and are more precise than previously reported results. The measurements also revealed continuous sub‐milliseconds proton spills at a low dose rate for the synchrotron accelerator and radiofrequency pulses at 7 µs and 1 ms repetition time for the synchrocyclotron accelerator.ConclusionThe AdvaPIX‐Timepix3 detector can be used to directly measure and monitor time structures on microseconds scale of the PBS proton beam delivery. This method yielded results with high precision and is completely independent of the machine log files.

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Definition of dose rate for FLASH pencil‐beam scanning proton therapy: A comparative study

Cited by 2 publications

References 23 publications

Navigating the straits: realizing the potential of proton FLASH through physics advances and further pre-clinical characterization

Navigating the straits: realizing the potential of proton FLASH through physics advances and further pre-clinical characterization

Time structures of proton pencil beam scanning delivery on a microsecond scale measured with a pixelated semiconductor detector Timepix3

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