Determining the energy spectrum of clinical linear accelerator using an optimized photon beam transmission protocol

Choi, Hyun Joon; Park, Hyojun; Yi, Chul Young; Kim, Byoung Chul; Shin, Wook; Min, Chul Hee

doi:10.1002/mp.13569

Cited by 7 publications

(6 citation statements)

References 45 publications

(71 reference statements)

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“…The X-ray spectrum of the 150 kVp source was simulated using the XRayGUI (Version 1.4.2.0, BAM Federal Institute for Materials Research and Testing, Berlin, Germany) matching experimental conditions as closely as possible. For the X-ray spectrum of the 6 MV source, already published particle fluence within a water phantom from a Varian Linac was extracted from Choi et al (2019) 82 . Proton simulations with a 100 (±1%) MeV beam were performed on a CentOS7 Linux distribution on the hpc Euler cluster of ETHZ using TOPAS version 3.7 and triplicates of 3.33 × 10 5 histories.…”

Section: Methodsmentioning

confidence: 99%

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

et al. 2022

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Nanoparticle-based radioenhancement is a promising strategy for extending the therapeutic ratio of radiotherapy. While (pre)clinical results are encouraging, sound mechanistic understanding of nanoparticle radioenhancement, especially the effects of nanomaterial selection and irradiation conditions, has yet to be achieved. Here, we investigate the radioenhancement mechanisms of selected metal oxide nanomaterials (including SiO2, TiO2, WO3 and HfO2), TiN and Au nanoparticles for radiotherapy utilizing photons (150 kVp and 6 MV) and 100 MeV protons. While Au nanoparticles show outstanding radioenhancement properties in kV irradiation settings, where the photoelectric effect is dominant, these properties are attenuated to baseline levels for clinically more relevant irradiation with MV photons and protons. In contrast, HfO2 nanoparticles retain some of their radioenhancement properties in MV photon and proton therapies. Interestingly, TiO2 nanoparticles, which have a comparatively low effective atomic number, show significant radioenhancement efficacies in all three irradiation settings, which can be attributed to the strong radiocatalytic activity of TiO2, leading to the formation of hydroxyl radicals, and nuclear interactions with protons. Taken together, our data enable the extraction of general design criteria for nanoparticle radioenhancers for different treatment modalities, paving the way to performance-optimized nanotherapeutics for precision radiotherapy.

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Section: Methodsmentioning

confidence: 99%

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

et al. 2022

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“…Direct measurement of X‐ray energy spectrum from a clinical linac is challenging because of the high photon fluence 2‐5 . As a result, several indirect techniques, such as Compton spectroscopy 6‐8 and transmission measurements 2,3,9‐12 were performed to obtain the energy spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…Direct measurement of X‐ray energy spectrum from a clinical linac is challenging because of the high photon fluence. 2 , 3 , 4 , 5 As a result, several indirect techniques, such as Compton spectroscopy 6 , 7 , 8 and transmission measurements 2 , 3 , 9 , 10 , 11 , 12 were performed to obtain the energy spectrum. In Compton spectroscopy, the energy spectrum of the Compton scattered photons was measured at an arbitrary scatter angle, and the energy spectrum of the primary photons was reconstructed using the Klein–Nishina formula.…”

Section: Introductionmentioning

confidence: 99%

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Direct energy spectrum measurement of X‐ray from a clinical linac

Suda

Hariu

Yamauchi

et al. 2021

J Applied Clin Med Phys

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A realistic X‐ray energy spectrum is essential for accurate dose calculation using the Monte Carlo (MC) algorithm. An energy spectrum for dose calculation in the radiation treatment planning system is modeled using the MC algorithm and adjusted to obtain acceptable agreement with the measured percent depth dose (PDD) and off‐axis ratio. The simulated energy spectrum may not consistently reproduce a realistic energy spectrum. Therefore, direct measurement of the X‐ray energy spectrum from a linac is necessary to obtain a realistic spectrum. Previous studies have measured low photon fluence directly, but the measurement was performed with a nonclinical linac with a thick target and a long target‐to‐detector distance. In this study, an X‐ray energy spectrum from a clinical linac was directly measured using a NaI(Tl) scintillator at an ultralow dose rate achieved by adjusting the gun grid voltage. The measured energy spectrum was unfolded by the Gold algorithm and compared with a simulated spectrum using statistical tests. Furthermore, the PDD was calculated using an unfolded energy spectrum and a simulated energy spectrum was compared with the measured PDD to evaluate the validity of the unfolded energy spectrum. Consequently, there was no significant difference between the unfolded and simulated energy spectra by nonparametric, Wilcoxon's rank‐sum, chi‐square, and two‐sample Kolmogorov–Smirnov tests with a significance level of 0.05. However, the PDD calculated from the unfolded energy spectrum better agreed with the measured compared to the calculated PDD results from the simulated energy spectrum. The adjustment of the incident electron parameters using MC simulation is sensitive and takes time. Therefore, it is desirable to obtain the energy spectrum by direct measurement. Thus, a method to obtain the realistic energy spectrum by direct measurement was proposed in this study.

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“…Faddegon et al [26] decreased the mA of a clinical linear accelerator by several orders of magnitude, and used a pulse mode detector to measure the output spectrum. The most common technique for spectrum measurement involved unfolding an energy spectrum from measurements of beam transmission through various mass thicknesses of attenuating material [8] [27]- [34]. A photon energy spectrum can be subsequently unfolded from the transmission measurements using a wide variety of unfolding techniques, including Laplace transform pairs [3] [27] [31], direct matrix inversion [33], and neural networks [32].…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Energy Spectrum of a 6 MV Linear Accelerator Using Compton Scattering Spectroscopy and Monte Carlo-Generated Corrections

Taneja¹,

Bartol²,

Culberson³

et al. 2020

IJMPCERO

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Purpose: The energy spectrum of a linear accelerator used for dose calculations is determined during beam commissioning by iteratively adjusting the spectrum and comparing calculated and measured percent depth-dose curves. Direct measurement of the energy spectrum using pulse mode detectors is particularly challenging because of the high-energy, high fluence nature of these beams and limitations of the detector systems. This work implements a Compton scattering (CS) spectroscopy setup and presents detector corrections and spectral unfolding techniques to measure the spectrum of a 6 MV linear accelerator using a pulse mode detector. Methods: Spectral measurements were performed using a Varian Clinac 21EX linear accelerator and a high-purity germanium (HPGe) detector. To reduce fluence to the detector, a custom-built lead shield and a CS spectrometry setup were used. The detector was placed at CS angles of 46˚, 89˚, and 125˚. At each of these locations, a detector response function was generated to account for photon interactions within the experimental geometry. Gold's deconvolution algorithm was used to unfold the energy spectrum. The measured spectra were compared to simulated spectra, which were obtained using an experimentally benchmarked model of the Clinac 21EX in MCNP6. Results: Measurements were acquired and detector response corrections were calculated for all three CS angles. A comparison of spectra for all CS angles showed good agreement with one another. The spectra for all three angles were averaged and showed good agreement with the MCNP6 simulated spectrum, with all points above 400 keV falling within 4%, which was within the uncertainty of the measurement and statistical uncertainty. Conclusions: The measurement of the energy spectrum of a 6 MV linear accelerator using a pulse-mode detector is pre-

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Determining the energy spectrum of clinical linear accelerator using an optimized photon beam transmission protocol

Cited by 7 publications

References 45 publications

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

Direct energy spectrum measurement of X‐ray from a clinical linac

Measurement of the Energy Spectrum of a 6 MV Linear Accelerator Using Compton Scattering Spectroscopy and Monte Carlo-Generated Corrections

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