KMID : 1038620120300010002
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Radiation Oncology Journal 2012 Volume.30 No. 1 p.2 ~ p.35
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The effect of photon energy on intensity-modulated radiation therapy (IMRT) plans for prostate cancer
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Sung Won-Mo
Park Jong-Min Choi Chang-Heon Ha Sung-Whan Ye Sung-Joon
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Abstract
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Purpose: To evaluate the effect of common three photon energies (6-MV, 10-MV, and 15-MV) on intensity-modulated radiation therapy (IMRT) plans to treat prostate cancer patients.
Materials and Methods: Twenty patients with prostate cancer treated locally to 81.0 Gy were retrospectively studied. 6-MV, 10-MV, and 15-MV IMRT plans for each patient were generated using suitable planning objectives, dose constraints, and 8-fi eld setting. The plans were analyzed in terms of dose-volume histogram for the target coverage, dose conformity, organs at risk (OAR) sparing, and normal tissue integral dose.
Results: Regardless of the energies chosen at the plans, the target coverage, conformity, and homogeneity of the plans were similar. However, there was a signifi cant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV. The V20 Gy of rectal wall with 6-MV, 10-MV, and 15-MV were 95.6%, 88.4%, and 89.4% while the mean dose to femoral heads were 31.7, 25.9, and 26.3 Gy, respectively. Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%. Overall, integral doses in mid and low dose regions in 6-MV plans were increased by up to 13%.
Conclusion: In this study, 10-MV prostate IMRT plans showed better OAR sparing and less integral doses than the 6-MV. The biological and clinical signifi cance of this fi nding remains to be determined afterward, considering neutron dose contribution
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KEYWORD
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Intensity-modulated radiation therapy, Prostate cancer, Photon energy, Treatment planning, Integral dose
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