Journal of Medical Physics
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Year : 2020  |  Volume : 45  |  Issue : 2  |  Page : 78-87

Evaluation of dose distribution and normal tissue complication probability of a combined dose of cone-beam computed tomography imaging with treatment in prostate intensity-modulated radiation therapy

1 Graduate School of Comprehensive Human Sciences, University of Tsukuba; Department of Radiology, University of Tsukuba Hospital, Ibaraki, Japan
2 Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
3 Department of Radiology, Chiba University Hospital, Chiba, Japan
4 Faculty of Health Sciences, Juntendo University, Tokyo, Japan
5 Department of Radiology, University of Tsukuba Hospital, Ibaraki, Japan

Correspondence Address:
Prof. Tomonori Isobe
1-1-1 Tennodai, Tsukuba, Ibaraki
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jmp.JMP_4_20

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Purpose: The purpose of this study is to evaluate the effects of cone-beam computed tomography (CBCT) on dose distribution and normal tissue complication probability (NTCP) by constructing a comprehensive dose evaluation system for prostate intensity-modulated radiation therapy (IMRT). Methods: A system that could combine CBCT and treatment doses with MATLAB was constructed. Twenty patients treated with prostate IMRT were studied. A mean dose of 78 Gy was prescribed to the prostate region, excluding the rectal volume from the target volume, with margins of 4 mm to the dorsal side of the prostate and 7 mm to the entire circumference. CBCT and treatment doses were combined, and the dose distribution and the NTCP of the rectum and bladder were evaluated. Results: The radiation dose delivered to 2% and 98% of the target volume increased by 0.90 and 0.74 Gy on average, respectively, in the half-fan mode and on average 0.76 and 0.72 Gy, respectively, in the full-fan mode. The homogeneity index remained constant. The percent volume of the rectum and bladder irradiated at each dose increased slightly, with a maximum increase of <1%. The rectal NTCP increased by approximately 0.07% from 0.46% to 0.53% with the addition of a CBCT dose, while the maximum NTCP in the bladder was approximately 0.02%. Conclusions: This study demonstrated a method to evaluate a combined dose of CBCT and a treatment dose using the constructed system. The combined dose distribution revealed increases of <1% volume in the rectal and bladder doses and approximately 0.07% in the rectal NTCP.

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