Angular correction in reconstruction of electron spectra from depth dose distributions

Chvetsov, A; Sandison, George A.

doi:10.1118/1.1592031

Cited by 12 publications

(9 citation statements)

References 5 publications

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“…The effective algorithms to estimate the dose contribution of treatment head bremsstrahlung to electron beam dose distributions in patients have been previously developed by Faddegon and Bleves 4 and Deng et al 5 The influence of the initial angular spread of incident electrons on the reconstructed spectra was estimated and discussed in our previous article. 9 Therefore, we restrict our discussion to spectral reconstruction based only on depth doses of monodirectional and normally incident electrons on a semi-infinite water medium and hence do not consider the initial angular spread of the electron beam or bremsstrahlung photons coming from treatment head. This restriction adequately serves our purpose to illustrate the essence of the proposed adaptive regularization technique.…”

Section: A Variational Methods With Adaptive Regularizationmentioning

confidence: 99%

Reconstruction of electron spectra from depth doses with adaptive regularization

2006

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Electron spectral reconstruction of medical accelerators from measured depth doses is a practical method for providing the input initial phase space distribution at the patient surface that is required by Monte Carlo treatment planning systems. The posed inverse problem of spectral reconstruction is ill conditioned and this may lead to nonphysical oscillations in the reconstructed spectra. Use of a variational method of solution with a regularization technique removes the oscillations but tends to smooth the sharp (deltalike) energy peak that is a common feature in electron spectra generated by medical accelerators. Because the sharp peak contains a large percentage of the electrons in the spectrum, an accurate estimate of the peak width, height and position is critical to the success of the technique for spectrum reconstruction with regularization. We propose use of an adaptive regularization term as a special form of the general Tichonov regularization function. The variational method with the adaptive regularization term is applied to reconstruct electron spectra for the 6, 9, and 18 MeV electron beams of a Varian Clinac 2100C accelerator and proves to be a very simple, effective and accurate approach. Results using this variational method with adaptive regularization almost perfectly reconstruct electron spectra from depth dose distributions.

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Section: A Variational Methods With Adaptive Regularizationmentioning

confidence: 99%

Reconstruction of electron spectra from depth doses with adaptive regularization

2006

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“…El conocimiento del haz clínico de radiación es esencial en dosimetría [1], en la planificación del tratamiento [1,2], en garantia de calidad, en el diseño de un acelerador lineal [3] y en simulaciones realistas del haz [4]. La planificación del tratamiento del cáncer puede ser elaborada correctamente solo si las características del haz son conocidas.…”

Section: Introductionunclassified

Sobre La Posibilidad De Usar El Método De Regularización De Tikhonov Para Reconstruir El Espectro De Energía De Un Haz Clínico De Electrones

Wilches¹,

Apaza²,

Costa³

2020

Momento

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ResumenEn radioterapia, el espectro de energía de electrones es la característica más importante para modelar la fuente de radiación cuando el propósito es el cálculo exacto de la dosis. Usualmente, se exploran tres métodos para obtener el espectro: (i) simulación de la fuente vía Monte Carlo; (ii) medición directa vía un espectrómetro magnético y (iii) reconstrucción inversa. Entre ellos, esteúltimo es considerado como el más apropiado por su simplicidad, rapidez y eficacia, a pesar de no ser el más exacto. La reconstrucción inversa tiene por objeto extraer el espectro de energía a partir de la distribución de dosis en profundidad a través de la resolución de un problema mal definido, vía el método de regularización de Tikhonov. La idoneidad de la reconstrucción es evaluada usando elíndice gamma. Los resultados muestran que la regularización de Tikhonov es

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“…A influência do espalhamento angular inicial no espectro de energia dos elétrons incidentes também tem sido reportada 2,9 .…”

Section: Introductionunclassified

Determinação de Espectros de Energia de Elétrons Clínicos a partir de Curvas de Porcentagem de Dose em Profundidade (PDP) utilizando o Método de Recozimento Simulado Clássico

Visbal

Costa

2016

Rev Bras Fis Med

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ResumoAs curvas de porcentagem de dose em profundidade representam um conjunto importante de dados para feixes de elétrons pois descrevem claramente as propriedades dosimétricas destes. Usando uma teoria de transporte acurada ou o método Monte Carlo encontram-se diferenças obvias entre a PDP de feixes de elétrons monoenergéticos e a de feixes de elétrons clínicos à energia nominal do acelerador em um objeto simulador de água. Em radioterapia, o espectro de energia de elétrons deve ser considerado para aprimorar a acurácia do cálculo da dose toda vez que o feixe de elétrons que atinge a superfície do objeto simulador de água após atravessar às estruturas do acelerador e o ar, não é mais monoenergetico. Existem três abordagens principais para extrair o espectro de energia de elétrons desde curvas de PDP: Método Monte Carlo, Medição Direta e Reconstrução Inversa. Neste trabalho será apresentado o método de Recozimento Simulado Clássico como uma abordagem prática, consistente e simples de reconstrução inversa como sendo uma boa alternativa aos outros dois métodos. Palavras-chave: recozimento simulado; espectros de energia; elétrons; radioterapia; porcentagem de dose em profundidade; Matlab; otimização; PENELOPE. AbstractPercentage depth dose of electron beams represents an important item of data in radiation therapy treatment since it describes the dosimetric properties of these. Using an accurate transport theory, or the Monte Carlo method, has been shown obvious differences between the dose distribution of electron beams of a clinical accelerator in a water simulator object and the dose distribution of monoenergetic electrons of nominal energy of the clinical accelerator in water. In radiotherapy, the energy spectrum of electrons should be considered to improve the accuracy of dose calculation, because the electron beams that reach the surface traveling through internal structures of accelerator are not in fact monoenergetic. There are three principal approaches to obtain electron energy spectra from central PDP: Monte Carlo Method, Direct Measurement and Inverse Reconstruction. In this work, it will be presented the Simulated Annealing method as a practical, reliable and simple approach of inverse reconstruction as being an optimal alternative to other options.

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Angular correction in reconstruction of electron spectra from depth dose distributions

Cited by 12 publications

References 5 publications

Reconstruction of electron spectra from depth doses with adaptive regularization

Reconstruction of electron spectra from depth doses with adaptive regularization

Sobre La Posibilidad De Usar El Método De Regularización De Tikhonov Para Reconstruir El Espectro De Energía De Un Haz Clínico De Electrones

Determinação de Espectros de Energia de Elétrons Clínicos a partir de Curvas de Porcentagem de Dose em Profundidade (PDP) utilizando o Método de Recozimento Simulado Clássico

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