Absorbed dose calorimetry

Renaud, James; Sarfehnia, Arman; Seuntjens, Jan

doi:10.1088/1361-6560/ab4f29

Cited by 30 publications

(41 citation statements)

References 222 publications

(258 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, in GSI Caves A and M they rely on the usage of ionization chambers as it is the standard method in particle therapy, which is the main background of the research activities performed. In addition, recent water calorimetry experiments have shown good agreement with the ionization chamber concept [21,22].…”

Section: Beam Monitor Calibrationmentioning

confidence: 73%

Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

et al. 2020

View full text Add to dashboard Cite

Section: Beam Monitor Calibrationmentioning

confidence: 73%

Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

et al. 2020

View full text Add to dashboard Cite

“…The most common absorbing mediums are water and graphite and for either medium, thermal isolation (and hence long thermal time constants) is very desirable to minimize the corrections required for conductive heat loss. For a review of absorbed dose calorimetry see Renaud et al [40].…”

Section: Calorimetermentioning

confidence: 99%

Calorimeter for Real-Time Dosimetry of Pulsed Ultra-High Dose Rate Electron Beams

et al. 2020

View full text Add to dashboard Cite

An aluminum calorimeter was investigated as a possible real-time dosimeter for electron beams with an ultra-high dose per pulse (DPP), as used in FLASH radiation therapy (a few Gy/pulse). Ionization chambers, the most widely used active dosimeter type in conventional external beam radiation therapy, suffer from large ion recombination losses at these conditions. Passive dosimeters, such as alanine, are independent of dose rate but do not provide real-time read-out. In this work it is shown that the response of alanine is independent of the DPP in the investigated ultra-high DPP range (up to 2.3 Gy/pulse). Alanine dose measurements were then used to determine the ion recombination correction for an Advanced Markus plane-parallel ionization chamber at ultra-high DPP. Ion collection losses larger than 50% were observed. Therefore, ionization chambers are not considered suitable for accurate dosimetry in FLASH radiation therapy. As an alternative, in a second (independent) experiment an aluminum open-to-atmosphere calorimeter, operated in the quasi-adiabatic mode was investigated at ultra-high DPP electron radiation. The beam pulse charge, and thus the DPP, was varied to evaluate the linearity of the calorimeter response in the DPP range between 0.3 and 1.8 Gy/pulse. On average, the standard deviation of the calorimeter response was 0.1%. The response was proportional to the DPP in the investigated range. The average deviation of the linear fit of the calorimeter dose as a function of the beam pulse charge was <0.5%. This preliminary investigation suggests that a simplified calorimeter design is suitable as a dosimeter with real-time read-out for clinical FLASH radiation therapy beams.

show abstract

“…[20][21][22][23][24][25][26][27][28] Even among primary standards, absorbed dose calorimetry is considered the most direct and absolute method of determining absorbed dose to water since device calibration can be achieved in terms of quantities with traceable standards (i.e., electrical and temperature), entirely independent of radiation. [29][30][31][32] Thus, calorimetry-based measurements can form the basis of a direct absorbed dose calibration of an IC in the clinically relevant field, or a derivation of their correction factors (e.g., k B ) for those beams.…”

Section: Introductionmentioning

confidence: 99%

Absolute dosimetry of a 1.5 T MR‐guided accelerator‐based high‐energy photon beam in water and solid phantoms using Aerrow

et al. 2020

View full text Add to dashboard Cite

Purpose In this work, the fabrication, operation, and evaluation of a probe‐format graphite calorimeter — herein referred to as Aerrow — as an absolute clinical dosimeter of high‐energy photon beams while in the presence of a B = 1.5 T magnetic field is described. Comparable to a cylindrical ionization chamber (IC) in terms of utility and usability, Aerrow has been developed for the purpose of accurately measuring absorbed dose to water in the clinic with a minimum disruption to the existing clinical workflow. To our knowledge, this is the first reported application of graphite calorimetry to magnetic resonance imaging (MRI)‐guided radiotherapy. Methods Based on a previously numerically optimized and experimentally validated design, an Aerrow prototype capable of isothermal operation was constructed in‐house. Graphite‐to‐water dose conversions as well as magnetic field perturbation factors were calculated using Monte Carlo, while heat transfer and mass impurity corrections and uncertainties were assessed analytically. Reference dose measurements were performed in the absence and presence of a B = 1.5 T magnetic field using Aerrow in the 7 MV FFF photon beam of an Elekta MRI‐linac and were directly compared to the results obtained using two calibrated reference‐class IC types. The feasibility of performing solid phantom‐based dosimetry with Aerrow and the possible influence of clearance gaps is also investigated by performing reference‐type dosimetry measurements for multiple rotational positions of the detector and comparing the results to those obtained in water. Results In the absence of the B‐field, as well as in the parallel orientation while in the presence of the B‐field, the absorbed dose to water measured using Aerrow was found to agree within combined uncertainties with those derived from TG‐51 using calibrated reference‐class ICs. Statistically significant differences on the order of (2–4)%, however, were observed when measuring absorbed dose to water using the ICs in the perpendicular orientation in the presence of the B‐field. Aerrow had a peak‐to‐peak response of about 0.5% when rotated within the solid phantom regardless of whether the B‐field was present or not. Conclusions This work describes the successful use of Aerrow as a straightforward means of measuring absolute dose to water for large high‐energy photon fields in the presence of a 1.5 T B‐field to a greater accuracy than currently achievable with ICs. The detector‐phantom air gap does not appear to significantly influence the response of Aerrow in absolute terms, nor does it contribute to its rotational dependence. This work suggests that the accurate use of solid phantoms for absolute point dose measurement is possible with Aerrow.

show abstract

Absorbed dose calorimetry

Cited by 30 publications

References 222 publications

Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

Calorimeter for Real-Time Dosimetry of Pulsed Ultra-High Dose Rate Electron Beams

Absolute dosimetry of a 1.5 T MR‐guided accelerator‐based high‐energy photon beam in water and solid phantoms using Aerrow

Contact Info

Product

Resources

About