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KMID : 0362919950130040397
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Journal of the Korean Society for Therapeutic Radiology and Oncology
1995 Volume.13 No. 4 p.397 ~ p.402
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The Study of Tissue Dose Perturbation by Air Cavity with 6MV Photon Beam
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Shin Byung-Chul
Yoo Myung-Jin
Moon Chang-Woo
Yum Ha-Yong
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Abstract
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Purpose: To determine the perturbation effect in the tissue downstream from surface layers of lesions located in the air/tumor-tissue interface of larynx using 6MV photon beam.
Materials and Methods: Thermoluminescent dosimeters(TLDs). Were embedded at 3 measurement locations in slab no.7 of a humanoid phantom and exposed to forward and backward direction using various field sizes(4 X 4cm2 ?15 X 15 cm2 ).
Results: At the air/tissue interface, forward dose perturbation factor(FDPF) is about 1.085 with 4 X 4 cm2 , 1.05 with 7 X 7 cm2 , 1.048 with 10 X 10 cm2 , and 1.041 with 15 X 15 cm2 . Backscatter dose perturbation factor(BDPF) is about 0.99 with 4 X 4 cm2 , 0.981 with 7 X 7 cm2 , 0.956 with 10 X 10 cm2 and 0.97 with 15 X 15 cm2 .
Conclusion: FDPF is greater as field size is smaller. And FDPF is smaller as the distance is further from the air/tissue interface.
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KEYWORD
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Dose perturbation, Air/tissue interface, Larynx
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