Measurement of Linac Thick-Target Bremsstrahlung Spectra Using a Large NaI Scintillation Spectrometer

Sandifer, C.W.; Taherzadeh, M.

doi:10.1109/tns.1968.4325064

Cited by 18 publications

(4 citation statements)

References 9 publications

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“…2. The FLUKA calculated PDD was carried out by simulating a 0.4 9 0.4 9 0.4 m 3 water phantom that consisted of 0.002 9 0.01 9 0.01 m 3 water dosimeters irradiated by a conical photon beam. The dosimeters were rectangular sheets set at varying depths along the central axis, and the SSD of the beam source was 1 m.…”

Section: C Fluka Monte Carlo Simulationmentioning

confidence: 99%

“…Measurements of LINAC spectra with scintillation detectors have been carried out by multiple centers. [3][4][5] Furthermore, a measurement 6 of the photon energy spectrum at the maze entrance was taken with a hyper-pure germanium detector (HPGe) for a 6 MV LINAC beam with a field size of 2 9 2 cm 2 . In this latter case, the spectrum taken at a maze entrance with two turns ranged from a few keV up to 450 keV, with an average energy of about 150 keV.…”

Section: Introductionmentioning

confidence: 99%

“…The photon energy spectrum and radiation components at this location are required to achieve good dosimetric precision, 2 but few studies have determined the energy spectrum outside LINAC rooms. Measurements of LINAC spectra with scintillation detectors have been carried out by multiple centers 3–5 . Furthermore, a measurement 6 of the photon energy spectrum at the maze entrance was taken with a hyper‐pure germanium detector (HPGe) for a 6 MV LINAC beam with a field size of 2 × 2 cm 2 .…”

Section: Introductionmentioning

confidence: 99%

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Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

2020

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The determination of x-ray spectra near the maze entrance of linear accelerator (LINAC) rooms is challenging due to the pulsed nature of the LINAC source. Mathematical methods to account for pulse pileup have been examined. These methods utilize the highly periodic pulsing structure of the LINAC, differing from the effects of high-intensity radioactive sources. Methods: Sodium iodide (NaI) and plastic scintillation detectors were used to determine the energy spectra at different points near the maze entrance of a medical LINAC. Monte Carlo calculations of the energy distribution of scattered photons were used to simulate the energy spectrum at the maze entrance. The proposed algorithm uses the Monte Carlo code, FLUKA, to calculate a response function for both detectors. To determine the effects of the pileup in the spectra, the Poisson distribution was used, employing the average number of photons per pulse (l) interacting with the detector. The quantity, l, was obtained from the ratio of the number of events detected to the number of pulses delivered. The energy spectra at various distances from the maze entrance were measured using NaI and plastic scintillation detectors. From these measurements, the values of µ were calculated, and the pileup probability was determined. The FLUKA Monte Carlo code was used to calculate the spectrum at the maze entrance and the response matrices of the NaI and plastic scintillation detectors. The algorithm based on the Poisson distribution was applied to calculate the spectrum. Results: The agreement between the calculated and measured spectra was within the first standard deviation of the variance expected in µ. This agreement confirms that photons at the maze entrance have energies between 30 and 240 keV for a maze with three turns, with an average energy of around 85 keV. After pileup correction, the range of the pulse height distribution with the plastic scintillation detector, which has a low atomic number, was decreased (0 to 140 keV). In contrast, the range of the pulse height distribution with the NaI scintillation detector was closer to the photon spectrum (0 to 240 keV). Conclusions: The corrected spectrum demonstrates that using a FLUKA Monte Carlo code and an algorithm based on the Poisson distribution are effective methods in removing the distortion due to the pileup in LINAC spectra when measuring with NaI and plastic scintillation detectors. The agreement between the corrected and measured spectra indicates that Monte Carlo modeling can accurately determine the spectrum of a LINAC machine at the maze entrance.

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Section: C Fluka Monte Carlo Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

2020

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“…A medição direta do espectro de fluência de fótons é difícil de fazer no ambiente clínico, devido às altas taxas de doses entregues pelas unidades de tratamento clínico que conduzem ao empilhamento de pulsos no detector e saturação induzida pelo tempo morto, e devido também aos grandes intervalos de energia dos fótons produzidos que levam a uma eficiência baixa do detector. Detectores cintiladores de iodeto de sódio ou detectores semicondutores de germânio têm sido utilizados, no feixe direto 2,3,4 , ou por espectrometria Compton 5,6,7,8 , com objetivo de determinar estes espectros. Medições destes espectros usando espectrômetros Compton têm uma vantagem, pois o detector é mantido fora do feixe direto intenso.…”

Section: Introductionunclassified

Caracterização de um Espectrômetro Compton para Medição de Espectros de Feixes de Fótons de Energia Alta

Manrique

Costa

2019

Rev Bras Fis Med

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O método de espectrometria Compton apresenta-se como uma técnica eficiente para medição de espectros de feixes de fótons de energia alta que são produzidos em aceleradores lineares clínicos e unidades de radioterapia de Co-60, usadas em tratamento de pacientes com câncer. Neste trabalho foi feita a caracterização de um espectrômetro Compton com o objetivo de medir o espectro de altura de pulsos (PHS, do inglês Pulse Height Spectra) para uma unidade de Co-60 de uso clinico, com a finalidade de obter o espectro de fluência de fótons para posteriormente aplicar este método na medição e reconstrução do espectro de bremsstrahlung de um acelerador linear clínico. Previamente foi feita a caracterização de um detector de NaI(Tl), obtendo as funções de resposta em energia para o espectrômetro Compton. Aqui apresentamos a medição dos espectros de altura de pulsos em configuração Compton para energias de raios X de 70 a 100 kV com ângulo Compton de 90o, as quais foram feitas com o fim de obter a resposta do espectrômetro a estas energias, para depois disso medir o espectro de altura de pulsos para a unidade de Co-60 em diferentes ângulos Compton.

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Bremsstrahlung Spectrum Analysis by Activation Method (LYRA, DIBRE, REFUM)1–6

Nakamura

1980

Computer Techniques in Radiation Transport and Dosimetry

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Measurement of Linac Thick-Target Bremsstrahlung Spectra Using a Large NaI Scintillation Spectrometer

Cited by 18 publications

References 9 publications

Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

Caracterização de um Espectrômetro Compton para Medição de Espectros de Feixes de Fótons de Energia Alta

Bremsstrahlung Spectrum Analysis by Activation Method (LYRA, DIBRE, REFUM)1–6

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