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KMID : 0362919890070010123
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Journal of the Korean Society for Therapeutic Radiology and Oncology
1989 Volume.7 No. 1 p.123 ~ p.132
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A Study on Design and Application of Tissue Compensator for 6MV X-rays
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Chai Kyu-Young
Choi Eun-Kyung
Chung Woong-Ki
Kang Wee-Saing
Ha Sung-Whan
Park Charn-Il
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Abstract
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A radiation beam incident on an irregular or sloping surface produces the non-uniformity of absorbed dose. The use of a tissue compensator can partially correct this dose inhomogeneity.
The tissue compensator is designed based on the patient´s three dimensional contour. After required compensator thickness was determined according to tissue deficit at 25 ㎝× 25 ㎝ field size, 10 ㎝ depth for 6MV x-rays, tissue deficit was mapped by isoheight technique using laser beam system. Compensator was constructed along the designed model using 0.5 ㎜ lead sheet or 5 ㎜ acryl plate. Dosimetric verification were performed by film dosimetry using humanoid phantom. Dosimetric measurements were normalized to central axis full phantom readings for both compensated and non-compensated field. Without compensation, the percent differences in absorbed dose ranged as high as 12.1% along transverse axis, 16.8% along vertical axis. With the tissue compensators in place, the difference was reduced to 0∼4.3% Therefore, it can be concluded that the compensator system constructed by isoheihnt technique can produce good dose distribution with acceptable inhomogeneity, and such compensator system can be electively applied to clinical radiotherapy.
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KEYWORD
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6 MV X-ray, Compensator, Isoheight technique, Laser beam system
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