Verification of absolute ionization chamber dosimetry in a proton beam using carbon activation measurements

Nichiporov, D.

doi:10.1118/1.1568591

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…An alternative method that overcomes this problem is the use of activation measurements that can determine the fluence of a broad beam directly if the cross‐section for the formation of the isotope being quantified is known with sufficient accuracy. This method was demonstrated by Nichiporov using the cross‐section for the formation of 11 C in a scintillating polystyrene sample. Aside from this problem, the fluence‐based approach has the intrinsic disadvantage that the uncertainty on the stopping power enters directly in the overall uncertainty of the dose determination.…”

Section: Detectors For Measurements Of Absorbed Dose In Reference Conmentioning

confidence: 99%

Dose detectors, sensors, and their applications

Giordanengo

2018

Medical Physics

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This article is intended to present the different types of particle and radiation detectors available for applications in particle therapy. Several types of detectors and sensors exist for measurements of absorbed dose in reference and nonreference conditions and the ones in use for beam monitoring. Therefore, this manuscript focuses on the following applications: (a) primary methods for dosimetry in ion beams, (b) measurements of absorbed dose in realistic patient‐specific scenarios with different dose delivery configurations, and (c) beam monitoring. Water and graphite calorimeters, Faraday cups, ionization based gas detectors are described first, followed by the description of the protocols for proton and ion dosimetry. Then films, scintillator and solid‐state detectors are reviewed. Finally, several types of ionization chambers (large, pinpoint, arrays of chambers arranged in regular 1D or 2D pattern, parallel‐plate configuration with large integral electrodes or with anode segmented in strips or pixels, multi‐wire, and the multi‐gap prototype) have been considered. New beam monitors to deal with a wide range of intensity and pulsed beams expected from new accelerators, different dose fractionation and advanced delivery techniques are presented. The existing detectors available for particle therapy have been described taking into account the different requirements for devices used in reference and nonreference conditions and the ones designed for beam monitoring.

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Section: Detectors For Measurements Of Absorbed Dose In Reference Conmentioning

confidence: 99%

Dose detectors, sensors, and their applications

Giordanengo

2018

Medical Physics

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“…Sample activation measurements. Larsson and Sarby (1987) and Nichiporov (2003) demonstrated that accurate dosimetry of a proton beam can also be achieved using a sample activation measurement. To this end, a sample with a known number, N, of 12 C atoms is irradiated at the phantom surface.…”

Section: Faraday Cup Measurementsmentioning

confidence: 99%

“…To this end, a sample with a known number, N, of 12 C atoms is irradiated at the phantom surface. After an irradiation of time interval τ , the proton fluence can be derived from a measurement of the 11 C activity, A 0 , using 4π βγ -coincidence counting and known values of the 12 C(p, pn) 11 C reaction cross section, σ , and the decay constant, λ, of 11 C using the expression (Nichiporov 2003)…”

Section: Faraday Cup Measurementsmentioning

confidence: 99%

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Dosimetry for ion beam radiotherapy

et al. 2010

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Recently, ion beam radiotherapy (including protons as well as heavier ions) gained considerable interest. Although ion beam radiotherapy requires dose prescription in terms of iso-effective dose (referring to an iso-effective photon dose), absorbed dose is still required as an operative quantity to control beam delivery, to characterize the beam dosimetrically and to verify dose delivery. This paper reviews current methods and standards to determine absorbed dose to water in ion beam radiotherapy, including (i) the detectors used to measure absorbed dose, (ii) dosimetry under reference conditions and (iii) dosimetry under non-reference conditions. Due to the LET dependence of the response of films and solid-state detectors, dosimetric measurements are mostly based on ion chambers. While a primary standard for ion beam radiotherapy still remains to be established, ion chamber dosimetry under reference conditions is based on similar protocols as for photons and electrons although the involved uncertainty is larger than for photon beams. For non-reference conditions, dose measurements in tissue-equivalent materials may also be necessary. Regarding the atomic numbers of the composites of tissue-equivalent phantoms, special requirements have to be fulfilled for ion beams. Methods for calibrating the beam monitor depend on whether passive or active beam delivery techniques are used. QA measurements are comparable to conventional radiotherapy; however, dose verification is usually single field rather than treatment plan based. Dose verification for active beam delivery techniques requires the use of multi-channel dosimetry systems to check the compliance of measured and calculated dose for a representative sample of measurement points. Although methods for ion beam dosimetry have been established, there is still room for developments. This includes improvement of the dosimetric accuracy as well as development of more efficient measurement techniques.

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“…Therefore, 11 C is produced in the irradiated tissue as a by-product of the radiotherapy with protons or heavy ions and its spatial distribution can be determined with a positron emission tomography (PET) camera during or after the treatment [32]. On the other hand, dosimetry of proton fields with activated graphite foils has been proposed as an alternative approach to ionization chamber based dosimetry [28]. Such applications in medical physics require an accurate knowledge of the nat C(p,x) 11 C cross section in the therapeutic energy range (proton energies up to 250 MeV) and suitable uncertainties for the accuracy required for radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

Experimental consolidation and absolute measurement of the $$^\text {nat}$$C(p,x)$$^{11}$$C nuclear activation cross section at 100 MeV for particle therapy physics

et al. 2021

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The $$^\text {nat}$$ nat C(p,x)$$^{11}$$ 11 C reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272–276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol https://doi.org/10.1088/1361-6560/ab4511, 2019) and Bäcker et al. (Nuclear Instrum Methods Phys Res B 454:50–55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68±3) mb is derived at (97±3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.

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Verification of absolute ionization chamber dosimetry in a proton beam using carbon activation measurements

Cited by 9 publications

References 14 publications

Dose detectors, sensors, and their applications

Dose detectors, sensors, and their applications

Dosimetry for ion beam radiotherapy

Experimental consolidation and absolute measurement of the $$^\text {nat}$$C(p,x)$$^{11}$$C nuclear activation cross section at 100 MeV for particle therapy physics

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