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KMID : 0362919950130040391
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Journal of the Korean Society for Therapeutic Radiology and Oncology
1995 Volume.13 No. 4 p.391 ~ p.396
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Dosimetric Characteristics on Penumbra Regions of the multileaf Collimator as Compared with the Lead Alloy Block
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Lee Sang-Wook
Oh Young-Taek
Kim Woo-Cheol
Keum Ki-Chang
Yoon Seong-Ick
Kim Hyun-Soo
Park Won
Chu Sung-Sil
Kim Gwi-Eon
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Abstract
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Purpose: The Conformal Radiation Therapy has been widely used under favour of development of computer technologies. The delivery of a large number of static radiation fields are being necessary for the conformal irradiation. In this paper, we investigate dosimetric characteristics on penumbra regions of a multileaf collimator(MLC), and compare to those of lead alloy block for he optimal use of the system in 3-D conformal radiotherapy.
Materials and Methods: The measurement of penumbra by MLC or lead alloy block was performed with 6 or 10 MV X-rays. The film was positioned at a dmax depth and 10 cm depth, and its optical density was determined using a scanning videodensitometer. The effective penumbra, the distance from 80% to 20% isodose lines and 90 to 10 were analyzed as a function of the angle between the direction of leaf motion and the edge defined by leaves.
Results: Increasing MLC angle (0-75°) was observed with increasing the penumbra widths and the scalloping effect. There was no definite differences of penumbra width from 80% to 20% isodose lines, while being the small increase of penumbra width of lead alloy block are agree reasonably with those of MLC within 4.8mm.
Conclusion: The comparative qualitative study of the penumbra between MLC and lead alloy block demonstrate the clinical acceptability and suitability of the multileaf collimator for 3-D conformal radiotherapy.
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KEYWORD
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Multileaf collimator, Effective penumbra, Film dosimetry
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