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The Effect of Aquaplast on Surface Dose of Photon Beam / 대한치료방사선과학회지
Journal of the Korean Society for Therapeutic Radiology ; : 95-100, 1995.
Artigo em Inglês | WPRIM | ID: wpr-6864
ABSTRACT

PURPOSE:

To evaluate the effect on surface dose due to Aquaplast used for immobilizing the patients with head and neck cancers in photon beam radiotherapy. MATERIALS AND

METHODS:

To assess surface and buildup region dose for 6MV X-ray from linear accelerator(Siemens Mevatron 6740), we measured percent ionization value with the Markus chamber model 30-329 manufactured by PTW Frieburg and Capintec electrometer, model WK92. For measurement of surface ionization value, the chamber was embedded in 25 X 25 X 3 cm3 acrylic phantom and set on 25 X 25 X 5 cm3, polystyrene phantom to allow adequate scattering. The measurements of percent depth ionization were made by placing the polystyrene layers of appropriate thickness over the chamber. The measurements were taken at 10 cm SSD for 5 X 5 cm2 , 10 X 10 cm2 , and 15 X 15 cm2 field sizes, respectively. Placing the layer of Aquaplast over the chamber, the same procedures were repeated. We evaluated two types o Aquaplast 1.6mm layer of original Aquaplast(manufactured by WFR Aquaplast Corp.) and transformed Aquaplast similar to moulded one for immobilizing the patients practically. We also measured surface ionization values with blocking tray in presence or absence of transformed Aquaplast. In calculating percent depth dose, we used the formula suggested by Gerbi and khan to correct overresponse of the Markus chamber.

RESULTS:

he surface doses for open fields of 5 X 5 cm2 , 10 X 10 cm2 , 15 X 15 cm2 were 7.9%, 13.6%, and 18.7% respectively. He original Aquaplast increased the surface doses upto 38.4%, 43.6% and 47.4% respectively. There were little differences in percent depth dose values beyond the depth of Dmax. Increasing field size, the blocking tray caused increase of the surface dose by 0.2%, 1.7%, 3.0% without Aquaplast, 0.2%, 1.9%, 3.7% with transformed Aquaplast, respectively.

CONCLUSION:

The original and transformed Aquaplast increased the surface dose moderately. The percent depth doses beyond Dmax, however, were not affected by Aquaplast. In conclusion, although the use of Aquaplast in practice may cause some increase of skin an dbuildup region dose, reduction of skin-sparing effect will not be so significant clinically.
Assuntos

Texto completo: DisponíveL Índice: WPRIM (Pacífico Ocidental) Assunto principal: Poliestirenos / Radioterapia / Sulfadiazina de Prata / Pele / Carboximetilcelulose Sódica / Cabeça / Pescoço Limite: Humanos Idioma: Inglês Revista: Journal of the Korean Society for Therapeutic Radiology Ano de publicação: 1995 Tipo de documento: Artigo

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Texto completo: DisponíveL Índice: WPRIM (Pacífico Ocidental) Assunto principal: Poliestirenos / Radioterapia / Sulfadiazina de Prata / Pele / Carboximetilcelulose Sódica / Cabeça / Pescoço Limite: Humanos Idioma: Inglês Revista: Journal of the Korean Society for Therapeutic Radiology Ano de publicação: 1995 Tipo de documento: Artigo