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KMID : 1164220040160010091
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Journal of Korean Society for Radiotherapeutic Technology
2004 Volume.16 No. 1 p.91 ~ p.99
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Dose distribution at junctional area abutting X-ray and electron fields
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Yang Gwang-Mo
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Abstract
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Purpose : For the head and neck radiotherapy, abutting photon field with electron field is frequently used for the irradiation of posterior neck when tolerable dose on spinal cord has been reached.
Materials and methods : Using 6 MV X-ray and 9 MeV electron beams of Clinac1800(Varian, USA) linear accelerator, we performed film dosimetry by the X-OMAT V film of Kodak in solid water phantom according to depths(0 cm, 1.5 cm, 3 cm, 5 cm). 6 MV X-ray and 9 MeV electron(1Gy) were exposes to 8cm depth and surface(SSD 100cm) of phantom. The dose distribution to the junction line between photon( field with block) and electron( field with block) fields was also measured according to depths(0 cm, 0.5 1.5 cm, 3 cm, 5 cm).
Results : At the junction line between photon and electron fields, the hot spot was developed on the side of the photon field and a cold spot was developed on that of the electron field. The hot spot in the photon side was developed at depth 1.5 cm with 7 mm width. The maximum dose of hot spot was increased to of reference doses in the photon field. The cold spot in the electron side was developed at all measured depths(0.5 cm-3 cm) with 1-12.5 mm widths. The decreased dose in the cold spot was of reference dose in the electron field.
Conclusion : When we make use of abutting photon field with electron field for the treatment of head and neck cancer we should consider the hot and cold dose area in the junction of photon and electron field according to location of tumor.
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KEYWORD
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X-ray, electron, head and neck cancer
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