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KMID : 1164220140260020289
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Journal of Korean Society for Radiotherapeutic Technology
2014 Volume.26 No. 2 p.289 ~ p.295
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Evaluation of Every Other Day - Cone Beam Computed Tomography in Image Guided Radiation Therapy for Prostate Cancer
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Park Byoung-Suk
Ahn Jong-Ho
Kim Jong-Sik
Song Gi-Won
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Abstract
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Purpose : Cone Beam Computed Tomography(CBCT) in Image Guided Radiation Therapy(IGRT), Set-up error can be reduced but exposure dose of the patient due to CBCT will increase. Through this study, we are to evaluate by making a scenario with the implementation period of CBCT as every other day.
Materials and Methods : Of prostate cancer patients, 9 patients who got a Intensity Modulated Radiation Therapy(IMRT) with CBCT in IGRT were analyzed. Based on values corrected by analyzing set-up error by using CBCT every day during actual treatment, we created a scenario that conducts CBCT every other day. After applying set-up error values of the day not performing CBCT in the scenario to the treatment planning system(Pinnacle 9.2, Philips, USA) by moving them from the treatment iso-center during actual treatment, we established re-treatment plan under the same conditions as actual treatment. Based on this, the dose distribution of normal organs and Planning Target Volume(PTV) was compared and analyzed.
Results : In the scenario that performs CBCT every other day based on set-up error values when conducting CBCT every day, average X-axis : 0.2 ± 0.73 ㎜, Y-axis : ０.1 ± 0.58 ㎜, Z-axis : -1.3 ± 1.17 ㎜ difference was shown. This was applied to the treatment planning to establish re-treatment plan and dose distribution was evaluated and as a result, Dmean : -0.17 Gy, D99% : -0.71 Gy of PTV difference was shown in comparison with the result obtained when carrying out CBCT every day. As for normal organs, V66 : 1.55% of rectal wall, V66 : -0.76% of bladder difference was shown.
Conclusion : In case of a CBCT perform every other day could reduce exposure dose and additional treatment time. And it is thought to be able to consider the application depending on the condition of the patient because the difference in the dose distribution of normal organs, PTV is not large.
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KEYWORD
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Cone Beam Computed Tomography(CBCT), Image Guided Radiation Therapy(IGRT), Prostate cancer, Set-up error
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