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KMID : 1164220060180020089
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Journal of Korean Society for Radiotherapeutic Technology
2006 Volume.18 No. 2 p.89 ~ p.96
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A Study of Heterogeneity Corrections for Radiation Treatment Planning
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Lee Je-Hee
Kim Bo-Gyum
Park Heung-Deuk
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Abstract
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Purpose: To study effectiveness of heterogeneity correction of internal-body inhomogeneities and patient positioning immobilizers in dose calculation, using images obtained from CT-Simulator.
Materials and Methods: A water phantom() was fabricated and, to simulate various inhomogeneity, 1) bone 2) metal 3) contrast media 4) immobilization devices(Head holder/pillow/Vac-lok) were inserted in it. And then, CT scans were peformed. The CT-images were input to Radiation Treatment Planning System(RTPS) and the MUs, to give 100 cGy at 10 cm depth with isocentric standard setup(Field Size=, SAD=100 cm), were calculated for various energies(4, 6, 10 MV X-ray). The calculated MUs based on various CT-images of inhomogeneities were compared and analyzed.
Results: Heterogeneity correction factors were compared for different materials. The correction factors were for bone, for metal materials, for contrast media, for Head-holder, for Head holder+pillow, and for Vac-lok.
Conclusion: It is revealed that the heterogeneity correction factor calculated from internal-body inhomogeneities have various values and have no consistency. and with increasing number of beam ports, the differences can be reduced to under 1%, so, it can be disregarded. On the other hand, heterogeneity correction from immobilizers must be regarded enough to minimize inaccuracy of dose calculation.
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KEYWORD
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heterogeneity correction, internal-body inhomogeneities, immobilizers
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