Estimation of focal and extra-focal radiation profiles based on Gaussian modeling in medical linear accelerators

Anai, Satoshi; Arimura, Hidetaka; Nakamura, Katsumasa; Araki, Fujio; Matsuki, Takaomi; Yoshikawa, Hiroyuki; Yoshidome, Satoshi; Shioyama, Yoshiyuki; Honda, Hiroshi; Ikeda, Nobuo

doi:10.1007/s12194-011-0118-1

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…A divergent primary beam with a number of rays produced from the X-ray focal spot of the linear accelerator was virtually delivered to the planning CT image. The X-ray focal spot was estimated based on an actual focal spot size of 1.53 mm [19,20] and a primary collimator angle of 13.9 • . Algorithm 2 shows an algorithm for the production of the planning PDI.…”

Section: Calculation Of the Planning Pdimentioning

confidence: 99%

A computerized framework for monitoring four-dimensional dose distributions during stereotactic body radiation therapy using a portal dose image-based 2D/3D registration approach

Nakamoto

Arimura

Nakamura

et al. 2015

Computerized Medical Imaging and Graphics

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A computerized framework for monitoring four-dimensional (4D) dose distributions during stereotactic body radiation therapy based on a portal dose image (PDI)-based 2D/3D registration approach has been proposed in this study. Using the PDI-based registration approach, simulated 4D "treatment" CT images were derived from the deformation of 3D planning CT images so that a 2D planning PDI could be similar to a 2D dynamic clinical PDI at a breathing phase. The planning PDI was calculated by applying a dose calculation algorithm (a pencil beam convolution algorithm) to the geometry of the planning CT image and a virtual water equivalent phantom. The dynamic clinical PDIs were estimated from electronic portal imaging device (EPID) dynamic images including breathing phase data obtained during a treatment. The parameters of the affine transformation matrix were optimized based on an objective function and a gamma pass rate using a Levenberg-Marquardt (LM) algorithm. The proposed framework was applied to the EPID dynamic images of ten lung cancer patients, which included 183 frames (mean: 18.3 per patient). The 4D dose distributions during the treatment time were successfully obtained by applying the dose calculation algorithm to the simulated 4D "treatment" CT images. The mean±standard deviation (SD) of the percentage errors between the prescribed dose and the estimated dose at an isocenter for all cases was 3.25±4.43%. The maximum error for the ten cases was 14.67% (prescribed dose: 1.50Gy, estimated dose: 1.72Gy), and the minimum error was 0.00%. The proposed framework could be feasible for monitoring the 4D dose distribution and dose errors within a patient's body during treatment.

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Section: Calculation Of the Planning Pdimentioning

confidence: 99%

A computerized framework for monitoring four-dimensional dose distributions during stereotactic body radiation therapy using a portal dose image-based 2D/3D registration approach

Nakamoto

Arimura

Nakamura

et al. 2015

Computerized Medical Imaging and Graphics

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“…This involves periodically checking the incident position and angle of the beam axis and the consistency of the beam profile, a method that has been described by Lutz et al [1] and Karzmark [2]. In previous research into X-ray irradiation used for external radiation therapy, the focal spot size of the electron beam incident on a target was measured using indirect methods involving a spot camera [3] or metallic thin slit [4] [5] [6] located outside the irradiation gantry head. This approach, however, makes it difficult to calculate the distribution of the accelerated electron beam before reaching the X-ray target, as the spread of the focal spot through this target can vary if it is not manufactured uniformly.…”

Section: Introductionmentioning

confidence: 99%

Direct Measurement of Medical Linear Accelerator Electron Beam Width at Scattering Foil Position

Shimozato¹,

Aoyama²

2017

IJMPCERO

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Purpose: The aim of this study was to develop a method for the direct measurement of electron beam width and distribution at the scattering foil on the carrousel in a medical linear accelerator gantry head, which differs from an existing indirect method for measuring the focal spot size using a camera or metallic slit located outside the gantry head. Methods: The electron beam emitted by the linear accelerator was used to irradiate radiochromic film mounted on the scattering foil on the carrousel, which was not used for clinical treatment. The electron beam width at the scattering foil position was then evaluated using the full width at half maximum of the Gaussian distribution approximated from each one-dimensional distribution of the irradiated radiochromic film. Results: The electron beam width at the scattering foil position was found to be 3.1 to 6.4 mm in the crossline direction and 2.8 to 5.5 mm in the inline direction with electron energy of 4 to 16 MeV. The two-dimensional distribution of the electron beam was therefore elliptical or distorted in shape, not circular. Conclusions: Direct measurement of the electron beam width at the scattering foil in the carrousel of a medical linear accelerator is possible, though the use of lower sensitivity film in addition to indirect methods is expected to bring about better results. However, as this method does not allow for direct measurement of the incident angle of the accelerated electron beam, further improvements and refinements are still needed.

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Ray Tracing Algorithm for Virtual Source Modeling based on Evaluation of Rounded Leaf End Effect of Multileaf Collimator

Zhou

Zhang

2015

IFMBE Proceedings

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Estimation of focal and extra-focal radiation profiles based on Gaussian modeling in medical linear accelerators

Cited by 4 publications

References 18 publications

A computerized framework for monitoring four-dimensional dose distributions during stereotactic body radiation therapy using a portal dose image-based 2D/3D registration approach

A computerized framework for monitoring four-dimensional dose distributions during stereotactic body radiation therapy using a portal dose image-based 2D/3D registration approach

Direct Measurement of Medical Linear Accelerator Electron Beam Width at Scattering Foil Position

Ray Tracing Algorithm for Virtual Source Modeling based on Evaluation of Rounded Leaf End Effect of Multileaf Collimator

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