Build-up cap materials for measurement of photon head-scatter factors

Weber, Lars; Nilsson, Per; Ahnesjö, Anders

doi:10.1088/0031-9155/42/10/002

Cited by 35 publications

(39 citation statements)

References 30 publications

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“…This agrees with the results obtained by Paul A. Jursinic,[21] L. Weber et al .,[44] and Hounsell et al . [29] The result of the present study confirms that build-up cap of high atomic number material causes much greater scatter of electrons[45] and above 10 × 10 cm 2 to 40 × 40 cm 2 field sizes maximum deviation which was less than 0.5% for 6MV-FB and 6MV-FFF and 0.7% for 10MV-FB and 10MV-FFF photon energies compared to low-Z mini phantoms measurements and reverse for less than 10 × 10 cm 2 field size.…”

Section: Discussionsupporting

confidence: 93%

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom

et al. 2014

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To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm2 to 40 × 40 cm2. The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques.

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Section: Discussionsupporting

confidence: 93%

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom

et al. 2014

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“…The atomic number of the material used in cylindrical buildup caps had been shown previously 11,30,35 to have an effect on the measurement of S c . So, it is not very surprising that the fabrication material of columnar miniphantoms would also affect the measurement of S c as shown previously 30 and in this work, Figs.…”

Section: Discussionmentioning

confidence: 97%

Measurement of head scatter factors of linear accelerators with columnar miniphantoms

Jursinic¹

2006

Med. Phys.

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The measurement of linear accelerator head scatter factors or in-air output factors, Sc, with columnar miniphantoms is refined in this work. Columnar miniphantoms are constructed from water equivalent materials: solid water and M3, and materials with higher mass density and atomic number: copper and lead. The change in the value of Sc from a 4-cm X 4-cm to a 40-cm X 40-cm field is different by 22% +/- 3%, 18% +/- 2%, and 10% +/- 3% for 6, 15, and 23 MV x rays, respectively, when measured with water equivalent or lead miniphantoms of 10 gm/cm2 depth. Based on measurements of transmission factors in solid-water miniphantoms of different depths, it is demonstrated that the beam energy spectra decreases in energy with increased field size. These changes in beam energy spectra alter the transmission and scatter of radiation and buildup of the dose in the miniphantom even if the miniphantom is made of water-equivalent material. These changes underlie the alteration in Sc when measured by miniphantoms fabricated from materials of different atomic number. It is shown that miniphantoms designed with a depth just adequate to stop contamination electrons will minimize these distortions due to transmission and scatter of radiation and buildup of dose in the miniphantom. Use of a miniphantom constructed from water-equivalent material with a depth appropriate for the x-ray energy being measured is the preferred method for determining Sc for dosimetry in water.

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“…The wall thickness of build-cup was sufficient to ensure the charged particle equilibrium [11,12]. The HSFs were measured for different clinical field sizes.…”

Section: Output Factorsmentioning

confidence: 99%

Photon beam commissioning of an Elekta Synergy linear accelerator

Mashud

Tariquzzaman

Alam

et al. 2017

Polish Journal of Medical Physics and Engineering

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The aim of this study is to present the results of commissioning of Elekta Synergy linear accelerator (linac). The acceptance test and commissioning were performed for three photon beams energies 4 MV, 6 MV and 15 MV and for the multileaf collimator (MLC). The percent depth doses (PDDs), in-plane and cross-plane beam profiles, head scatter factors (Sc), relative photon output factors (Scp), universal wedge transmission factor and MLC transmission factors were measured. The size of gantry, collimator, and couch isocenter were also measured.

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Build-up cap materials for measurement of photon head-scatter factors

Cited by 35 publications

References 30 publications

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom

Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom

Measurement of head scatter factors of linear accelerators with columnar miniphantoms

Photon beam commissioning of an Elekta Synergy linear accelerator

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