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KMID : 1164220140260010021
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Journal of Korean Society for Radiotherapeutic Technology
2014 Volume.26 No. 1 p.21 ~ p.28
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A Study on lung dose of Intensity modulated and volumetric modulated arc therapy plans using restricted angle of Non-small cell lung cancer
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Yeom Mi-Suk
Lee Woo-Suk
Kim Dae-Sup
Back Geum-Mun
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Abstract
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Purpose : For non-small cell lung cancer, if the treatment volume is large or the total lung volume is small, and the tumor is located in midline of patient’s body, total lung dose tends to increase due to tolerance dose of spinal cord. The purpose of this study is to compare and evaluate the total lung dose of three dimensional conformal radiotherapy(3D CRT), intensity modulated radiotherapy(IMRT) and volumetric modulated arc therapy(VMAT) using restricted angle for non-small cell lung cancer patients.
Materials and Methods : The treatment plans for four patients, being treated on TrueBeam STx(VarianTM, USA) with 10 MV and prescribed dose of 60 Gy in 30 fractions, 3D CRT, restricted angle IMRT and VAMT radiotherapy plans were established. Planning target volume(PTV), dose to total lung and spinal cord were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick’s index(PCI) for the PTV, V30, V20, V10, V5, mean dose for total lung and maximum dose for spinal cord was assessed.
Results : Average value of CI, HI and PCI for PTV was 0.944±0.009, 1.106±0.027 and 1.084±0.016 respectively. V20 values
from 3D CRT, IMRT and VMAT plans were 30.7%, 20.2% and 21.2% for the first patient, 33.0%, 29.2% and 31.5% for second
patient, 51.3%, 34.3% and 36.9% for third patient, finally 56.9%, 33.7% and 40.0% for the last patient. It was noticed that the
V20 was lowest in the IMRT plan using restricted angle. Maximum dose for spinal cord was evaluated to lower than the
tolerance dose.
Conclusion : For non-small cell lung cancer, IMRT with restricted angle or VMAT could minimize the lung dose and lower the dose to spinal cord below the tolerance level. Considering PTV coverage and tolerance dose to spinal cord, it was possible to obtain IMRT plan with smaller angle and this could result in lower dose to lung when compared to VMAT.
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KEYWORD
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Volumetric modulated arc therapy(VMAT), restricted angle, dose volume histogram (DVH), Paddick’s index(PCI)
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