High-Energy Electron Dose Perturbations in Regions of Tissue Heterogeneity

Boone, Max L. M.; Jardine, John H.; Wright, Ann E.; Tapley, Norah duV.

doi:10.1148/88.6.1136

Cited by 23 publications

(7 citation statements)

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“…The percent depth dose for the point is read from the depth-dose data in water for the electron-beam energy under consideration at the effective depth d eff and then corrected for the inverse-square law. CET, in general, varies with depth in the tissue and with beam energy (Almond et al, 1967;Boone et al, 1967). For lung tissue, the CET decreases with increasing depth and increases with increasing electron energy.…”

Section: B Tissue Heterogeneitiesmentioning

confidence: 99%

“…The problem of tissue heterogeneities is one of the major challenges of electron-beam dosimetry. Several investigators have reported the effect of heterogeneities on dose distribu- tion for electron beams Boone et al, 1967;Almond et al, 1967;Brenner et al, 1969;Pohlit, 1969). These studies showed that the magnitude of the dose perturbation depends on the shape, size, electron density (number of electrons/cm 3 ), and the effective atomic number of the heterogeneity.…”

Section: B Tissue Heterogeneitiesmentioning

confidence: 99%

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Clinical electron‐beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25

et al. 1991

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Section: B Tissue Heterogeneitiesmentioning

confidence: 99%

Section: B Tissue Heterogeneitiesmentioning

confidence: 99%

Clinical electron‐beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25

et al. 1991

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“…In electron beam therapy, tissue equivalent material bolus can be used and is normally placed in direct contact with patient skin 5,6,7 . It can be used to increase the dose at the surface when required, to flatten out an irregular surface, and to reduce the penetration of the electrons in parts of the field.…”

Section: Introductionmentioning

confidence: 99%

An investigation of central axis depth dose distribution perturbation due to an air gap between patient and bolus for electron beams

Kong

Holloway

2007

Australas. Phys. Eng. Sci. Med.

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Electron beams can be used for the radiotherapy treatment of superficial cancers. In many cases of electron beam radiotherapy, tissue equivalent bolus material placed on the skin is to be used to enhance skin dose. An air gap might be present between the bolus and the skin due to variation in the patient contour. The impact of semi-infinite air gaps under bolus material on central axis depth dose distributions for electron beams was investigated in this study. Semi-infinite air gaps were introduced between bolus and the surface of a water phantom for air gap sizes up to 20.0 mm and for bolus thicknesses of 5, 10 and 15 mm. The electron beams studied had nominal energies of 6, 10 and 14 MeV and circular fields of 3, 5, 7 and 9 cm diameter. Depth dose measurements were carried out in the water phantom with a Scanditronix p-Si electron diode. It was found that the impact of an air gap is dependent on beam energy, field size, air gap size and bolus thickness used. The impact of the air gap on central axis depth dose distribution increased with decreasing field size, increasing air gap size, decreasing electron beam energy and increasing bolus thickness. For 15 mm bolus, 3 cm diameter circular field, 6 MeV beam and the 20 mm air gap, the maximum dose and the surface dose was reduced by approximately 60% and the depth of dose maximum shifted 3.5 mm. An air gap between bolus and a patient should be avoided to ensure that there is no impact on the treatment. The measured data in this study can be used to determine the likely degree of impact on the treatment, of unavoidable air gaps between bolus and the patient.

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“…However, dose distributions with electrons may be significantly affected by tissue inhomogeneities within the target v o l~m e .~*~' Boone et al have measured a clinically significant dose reduction at the chest wall-lung interface only for 6 MeV electrons, but not for higher energies. 2 Ragnhult et al have studied dose distributions with 8, 10, 13, and 15 MeV electrons, and concluded that the 13 MeV energy was best suited to irradiate an internal mammary volume 30 mm thick, containing soft tissue, sternal bone and ribcartilage.22 Lindskoug and Hultborn studied anterior chest wall structures from autopsied patients with TLD dosimeters and concluded that electrons in the 10-13 MeV range could be employed in postmastectomy patients without the risk of underdosing internal mammary nodes. However, chest wall thickness in the eight cases studied was 30 mm or less, with the nodes being at a mean depth of 20 2 8 mm.l* Thus, the dose to the internal mammary area is not altered significantly by tissue inhomogeneities when electrons in the 10-15 MeV range are employed.…”

Section: Effects Of Tissue Inhomogeneity On Dose Distributionmentioning

confidence: 99%

“…However, any nodal tissue lying under rib or sternum could receive significantly less radiation with electrons, due to shielding by overlying bone. 2 Depth dose data must be determined for the electron generator actually employed: an electron beam of a stated energy may have different depth dose characteristics than a beam of the same stated energy from a different generator. Almeida and Almond have compared a Siemens Betatron and a Sagittaire Linear Accelerator, and demonstrated appreciable differences in dose distributions, surface dose, depth of maximum dose, and fall off slope for electron beams from the two units.'…”

Section: Effects Of Tissue Inhomogeneity On Dose Distributionmentioning

confidence: 99%

Computerized body tomography in breast cancer. I. Internal mammary nodes and radiation treatment planning

Munzenrider

Tchakarova

Castro

et al. 1979

Cancer

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The internal mammary area has been reviewed on CBT scans from 46 postmastectomy patients, and chest wall thicknesses computed there from the scan. Thicknesses ranged from 10 to 43 mm and 16 to 70 mm on the operated and nonoperated sides, and were weight-related in 38 modified mastectomy patients. Direct Cobalt and 15 MeV electron portals delivered 97-98% of the dose prescribed at 3 cm to a depth of 35 mm, the maximum average thickness on the operated side, while 12 and 10 MeV electrons gave 10 and 20% less at that depth. At 70 mm, underdosage with Cobalt and 15 MeV was 22% and 72%; insignificant doses were delivered with 10 and 12 MeV electrons. Routine determination of chest wall thickness is recommended in patients planned for electron beam treatment, in obese patients, and in patients treated with tangential photon techniques, to avoid underdosage to the internal mammary area. Internal mammary nodes were not routinely visualized, but abnormalities consistent with enlarged nodes were seen in six patients and gross recurrence in another.

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High-Energy Electron Dose Perturbations in Regions of Tissue Heterogeneity

Cited by 23 publications

References 0 publications

Clinical electron‐beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25

Clinical electron‐beam dosimetry: Report of AAPM Radiation Therapy Committee Task Group No. 25

An investigation of central axis depth dose distribution perturbation due to an air gap between patient and bolus for electron beams

Computerized body tomography in breast cancer. I. Internal mammary nodes and radiation treatment planning

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