Estimation of the focal spot size and shape for a medical linear accelerator by Monte Carlo simulation

Wang, Lilie L. W.; Leszczyński, Konrad

doi:10.1118/1.2426407

Cited by 44 publications

(31 citation statements)

References 17 publications

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“…The focal spot or source size is an important consideration in small fields (2). There are various methods to measure source size (47)(48)(49)(50), however it is beyond the scope of most clinical physicists. In such situation question lies as how sensitive is source size with respect to kΩ of a detector.…”

Section: Discussionmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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Section: Discussionmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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“…6 for determination of Gaussian parameters of the focal-spot radiation profile and the extra-focal radiation profile using narrow and broad total focal radiation profiles measured by slits with two widths. Gaussian models of the focal-spot radiation profile and the extra-focal radiation profile based on experimental data are useful and necessary for Monte Carlo simulations for estimating accurate dose distributions at penumbral area [3]. If the focal radiation profiles were incorrect, the dose profiles at the penumbral area obtained by the Monte Carlo simulation could not be consistent with measured data.…”

Section: Discussionmentioning

confidence: 98%

“…Wang and Leszczynski [3] reported that the dose profile penumbra depends on the X-ray focal-spot size and shape. Therefore, if the focal-spot size became wider, the dose profile penumbra would be larger.…”

Section: Introductionmentioning

confidence: 99%

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

Anai

Arimura

Nakamura

et al. 2011

Radiol Phys Technol

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The X-ray source or focal radiation is one of the factors that can degrade the conformal field edge in stereotactic body radiotherapy. For that reason, it is very important to estimate the total focal radiation profiles of linear accelerators, which consists of X-ray focal-spot radiation and extra-focal radiation profiles. Our purpose in this study was to propose an experimental method for estimating the focal-spot and extra-focal radiation profiles of linear accelerators based on triple Gaussian functions. We measured the total X-ray focal radiation profiles of the accelerators by moving a slit in conjunction with a photon field p-type silicon diode. The slit width was changed so that the extra-focal radiation could be optimally included in the total focal radiation. The total focal radiation profiles of an accelerator at 4-MV and 10-MV energies were approximated with a combination of triple Gaussian functions, which correspond to the focal-spot radiation, extra-focal radiation, and radiation transmitted through the slit assembly. As a result, the ratios of the Gaussian peak value of the extra-focal radiation to that of the focal spot for 4 and 10 MV were 0.077 and 0.159, respectively. The peak widths of the focal-spot and extra-focal radiation profiles were 0.57 and 25.0 mm for 4 MV, respectively, and 0.60 and 22.0 mm for 10 MV, respectively. We concluded that the proposed focal radiation profile model based on the triple Gaussian functions may be feasible for estimating the X-ray focal-spot and extra-focal radiation profiles.

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“…Test field B validates the primary focal spot size, shape, and location using the surrogate of penumbra 5 , 6 . Both the X and Y penumbra are evaluated.…”

Section: Methodsmentioning

confidence: 99%

Using a 2D detector array for meaningful and efficient linear accelerator beam property validations

Ritter

Gallagher

Roberson

2014

J Applied Clin Med Phys

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Following linear accelerator commissioning, the qualified medical physicist is responsible for monitoring the machine's ongoing performance, detecting and investigating any changes in beam properties, and assessing the impact of unscheduled repairs. In support of these responsibilities, the authors developed a method of using a 2D ionization chamber array to efficiently test and validate important linear accelerator photon beam properties. A team of three physicists identified critical properties of the accelerator and developed constancy tests that were sensitive to each of the properties. The result was a 14‐field test plan. The test plan includes large and small fields at varying depths, a reduced SSD field at shallow depth for sensitivity to extra focal photon and electron components, and analysis of flatness, symmetry, dose, dose profiles, and dose ratios. Constancy tests were repeated five times over a period of six weeks and used to set upper and lower investigation levels at ±.15em3 SDs. Deliberate variations in output, penumbra, and energy were tested to determine the suitability of the proposed method. Measurements were also performed on a similar, but distinct, machine to assess test sensitivity. The results demonstrated upper and lower investigation levels significantly smaller than the comparable TG‐142 annual recommendations, with the exception of the surrogate used for output calibration, which still fell within the TG‐142 monthly recommendation. Subtle changes in output, beam energy, and penumbra were swiftly identified for further investigation. The test set identified the distinct nature of the second accelerator. The beam properties of two photon energies can be validated in approximately 1.5 hrs using this method. The test suite can be used to evaluate the impact of minor repairs, detect changes in machine performance over time, and supplement other machine quality assurance testing.PACS numbers: 87.56bd, 87.56Fc

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Estimation of the focal spot size and shape for a medical linear accelerator by Monte Carlo simulation

Cited by 44 publications

References 17 publications

Small field dosimetry: What have we learnt?

Small field dosimetry: What have we learnt?

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

Using a 2D detector array for meaningful and efficient linear accelerator beam property validations

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