A prototype low-cost secondary standard calorimeter for reference dosimetry with ultra-high pulse dose rates

Bass, G A; Shipley, D R; Flynn, Samuel; Thomas, R.

doi:10.1259/bjr.20220638

Cited by 8 publications

(4 citation statements)

References 9 publications

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“…Bass et al 45 utilized a simple, low-cost secondary standard level calorimeter (SSC) physically resembling a Roos-type ionization chamber with a single sensing thermistor in the aluminium core. This instrument has been used in a converted clinical electron LINAC to deliver UHDR 6 MeV electron beam with an average dose rate of 180 Gy/s and 0.45 Gy/pulse.…”

Section: Calorimetrymentioning

confidence: 99%

Recent developments in absolute dosimetry for FLASH radiotherapy

Subiel

Romano

2023

BJR

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Ultra-high dose-rate (UHDR) irradiations, known as FLASH radiotherapy (RT), rely on delivery of therapeutic doses at instantaneous dose-rates several orders of magnitude higher than those currently used in conventional radiotherapy. It has been shown that such an extremely short delivery of radiation leads to remarkable reduction of normal tissue toxicity with respect to conventional dose-rate RT. However, dosimetry at UHDRs is complicated and it is essential to understand the effects that will influence detector response. To date, FLASH RT research has been focused on finding pragmatic solutions that allow the use of UHDR beams in the research setting, but there has been limited focus on absolute dosimetry utilizing primary and secondary standard devices. However, very recently the data on existing standard dosimeters and novel solutions which could serve as secondary standard devices in UHDR dosimetry started emerging. This review provides an overview of the studies that have been conducted employing calorimeters and innovative solutions utilizing ionization chambers.

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Section: Calorimetrymentioning

confidence: 99%

Recent developments in absolute dosimetry for FLASH radiotherapy

Subiel

Romano

2023

BJR

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“…Lye et al 18 used a graphite calorimeter, originally designed for higher energy electron beams, to carry out a similar measurement at the Australian Synchrotron, but the size of their calorimeter required a scanning method to deliver a uniform dose and this resulted in rather large uncertainty contributions. The design of Bass et al 19 is intended to be portable and therefore could potentially be used in a similar way to that of Lye et al However, graphite is inherently inhomogeneous, 20 due to its manufacturing process. Local density variations in graphite can be problematic, 21 particularly in this situation where the synchrotron beams are physically very small and the conversion factor from absorbed dose to graphite to absorbed dose to water is large in the 65−140 keV range of interest in this work.…”

Section: Introductionmentioning

confidence: 99%

“…used a graphite calorimeter, originally designed for higher energy electron beams, to carry out a similar measurement at the Australian Synchrotron, but the size of their calorimeter required a scanning method to deliver a uniform dose and this resulted in rather large uncertainty contributions. The design of Bass et al 19 . is intended to be portable and therefore could potentially be used in a similar way to that of Lye et al.…”

Section: Introductionmentioning

confidence: 99%

A novel calorimeter for synchrotron produced monochromatic x‐ray beams

2023

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BackgroundElectron synchrotrons produce x‐ray beams with dose rates orders of magnitude greater than conventional x‐ray tubes and with beam sizes on the order of a few millimeters. These characteristics put severe challenges on current dosimeters to accurately realize absorbed dose or air kerma.PurposeThis work seeks to investigate the suitability of a novel aluminum‐based calorimeter to determine absorbed dose to water with an uncertainty significantly smaller than currently possible with conventional detectors. A lower uncertainty in the determination of absolute dose rate would impact both therapeutic applications of synchrotron‐produced x‐ray beams and research investigations.MethodsA vacuum‐based calorimeter prototype with an aluminum core was built, matching the beam profile of the 140 keV monochromatic x‐ray beam, produced by the Canadian Light Source Biomedical Imaging and Therapy beamline. The choice of material and overall calorimeter design was optimized using FEM thermal modeling software while Monte Carlo radiation transport simulations were used to model the impact of interactions of the radiation beam with the detector components.ResultsCorrections for both the thermal conduction and radiation transport effects were of the order of 3% and the simplicity of the geometry, combined with the monochromatic nature of the incident x‐ray beam, meant that the uncertainty in each correction was ≤0.5%. The calorimeter performance was found to be repeatable over multiple irradiations of 1 Gy at the ± 0.6% level, and no systematic dependence on environmental effects or total dose was observed.ConclusionThe combined standard uncertainty in the determination of absorbed dose to aluminum was estimated to be 0.8%, indicating that absorbed dose to water, the ultimate quantity of interest, could be determined with an uncertainty on the order of 1%. This value is an improvement over current techniques used for synchrotron dosimetry and comparable with the state‐of‐the art for conventional kV x‐ray dosimetry.

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“…The Aerrow has so far been utilised within high-energy photon and electron beams, suggesting its potential usage with ultra-high dose per pulse beams [24][25][26]. Furthermore, the ion recombination losses experienced in ionisation chambers were addressed through the development of a prototype secondary standard calorimeter [27]. Developed at the NPL, this device utilises a single sensing core thermistor encased within a 3D-printed body mimicking the shape of a standard Roos-type chamber.…”

Section: Introductionmentioning

confidence: 99%

Proof-of-Principle of Absolute Dosimetry Using an Absorbed Dose Portable Calorimeter with Laser-Driven Proton Beams

McCallum,

Lee,

Milluzzo

et al. 2023

Applied Sciences

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Charged particle beams driven to ultra-high dose rates (UHDRs) have been shown to offer potential benefits for future clinical applications, particularly in the reduction of normal-tissue toxicity. Studies of the so-called FLASH effect have shown promise, generating huge interest in high dose rate radiation studies. With laser-driven proton beams, where the duration of the proton burst delivered to a sample can be as short as hundreds of picoseconds, the instantaneous dose rates are several orders of magnitude higher than those used for conventional radiotherapy. The dosimetry of these beam modalities is not trivial, with conventional active detectors, such as ionisation chambers, experiencing saturation effects making them unusable at the extremely high dose rates. Calorimeters, measuring the radiation-induced temperature rise in an absorber, offer an ideal candidate for the dosimetry of UHDR beams. However, their application in the measurement of laser-driven UHDR beams has so far not been trialled, and their effective suitability to work with the quasi-instantaneous and inhomogeneous dose deposition patterns and the harsh environment of a laser-plasma experiment has not been tested. The measurement of the absorbed dose of laser-driven proton beams was conducted in a first-of-its-kind investigation, employing the VULCAN-PW laser system of the Central Laser Facility (CLF) at the Rutherford Appleton Laboratory (RAL), using a small-body portable graphite calorimeter (SPGC) developed at the National Physical Laboratory (NPL) and radiochromic films. A small number of shots were recorded, with the corresponding absorbed dose measurements resulting from the induced temperature rise. The effect of the electromagnetic pulse (EMP) generated during laser–target interaction was assessed on the system, showing no significant effects on the derived signal-to-noise ratio. These proof-of-principle tests highlight the ability of calorimetry techniques to measure the absorbed dose for laser-driven proton beams.

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A prototype low-cost secondary standard calorimeter for reference dosimetry with ultra-high pulse dose rates

Cited by 8 publications

References 9 publications

Recent developments in absolute dosimetry for FLASH radiotherapy

Recent developments in absolute dosimetry for FLASH radiotherapy

A novel calorimeter for synchrotron produced monochromatic x‐ray beams

Proof-of-Principle of Absolute Dosimetry Using an Absorbed Dose Portable Calorimeter with Laser-Driven Proton Beams

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