Effects of beam modifiers and immobilization devices on the dose in the build-up region

Fontenla, Doracy P.; Napoli, J; Hunt, Margie; Fass, Daniel; McCormick, Beryl; Kutcher, Gerald J.

doi:10.1016/0360-3016(94)90537-1

Cited by 46 publications

(29 citation statements)

References 36 publications

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“…Since air-generated electrons dominate at extended SSD, the spectrum of the electrons is nearly independent of the distance from the source beyond 300 cm from the source. Thus, a single pencil-beam kernel, shown in Figure 9, can be used for calculating the dose due to electrons generated in air regardless of the distance from the source When a spoiler is inserted in the beam, most of the electrons originated in the accelerator head are absorbed in or scattered away by the spoiler [4,7,8]. Figure 7 shows that 1 cm water-equivalent material eliminates nearly all electrons produced upstream.…”

Section: Discussionmentioning

confidence: 99%

Doses near the surface during total-body irradiation with 15 MV X-rays

Kassaee¹,

Xiao²,

Bloch³

et al. 2001

Int. J. Cancer

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SUMMARY An extended source-surface distance (SSD) is often employed in total-body irradiation (TBI) to obtain fields sufficiently large to encompass the total body. It is clinically desirable to administer a uniform dose to all tissues, including the surface, especially to counteract the skin-sparing of high-energy X-rays. The electrons generated from the air contribute more to the dose near the surface at extended distances than at regular SSDs. However, if further increase of the dose at shallow depths is desired a spoiler can be employed. Monte Carlo simulations were used to study these effects for the electron component of the beam and the parameters needed for the pencil-beam dose calculation of this component. Measurements were performed to confirm these studies. The energy spectrum of electrons generated in air is independent of SSD. All the electrons in the beam, however, originate from the spoiler when one is used. The spectrum of these electrons is nearly independent of the SSD. The pencil-beam dose kernels were calculated using the derived electron spectra. To calculate doses in the buildup region with and without a spoiler, we use one pencil-beam kernel for the electrons generated in air and one for the electrons generated from the spoiler. Measured depth-dose data agreed with the calculation results.

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Section: Discussionmentioning

confidence: 99%

Doses near the surface during total-body irradiation with 15 MV X-rays

Kassaee¹,

Xiao²,

Bloch³

et al. 2001

Int. J. Cancer

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“…There have been recent changes in the direction of 3D-CRT with wedges, MLCs, compensators [13,43] or field-in-field techniques [26]. Breast IMRT is a further step toward an ideal solution [24].…”

Section: Planning Proceduresmentioning

confidence: 99%

“…The population was planning-favorable (PTV: 223-1,659 cm 3 ), but the planning time increased. OAR doses and total MU were not documented, but the physical wedge might increase lung and heart doses and increase MU/head leakage through longer beam-on time [12,13,43]. For ten just-planned patients fourand six-field hybrid IMRT, conventional, dynamic IMRT and field-in-field method were compared [27].…”

Section: Planning Proceduresmentioning

confidence: 99%

Multisegmented Tangential Breast Fields: a Rational Way to Treat Breast Cancer

et al. 2008

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“…The lack of electron equilibrium is a result of the reduced dose in the surface region, known as the skin-sparing effect. 1,2 It is imperative to describe the effect of scattering (e.g., wedge, block, tray) media on the surface dose. 2,3 The scattered radiation in the wedge fi lter contributes to doses outside the fi eld.…”

Section: Introductionmentioning

confidence: 99%