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| The depth dose characters of different tissue substitutes based on Eclipse |
| MIAO Li, QIU Zhengshuai, CHENG Xiaoguo |
| Radiotherapy Department, Qilu Hosipital of Shandong University, Jinan, 250012 China |
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Abstract Objective Researching the characters of depth dose deposition of different tissue substitutes.Methods The water phantom(20 cm×20 cm×20 cm)is built in Eclipse TPS, then different tissue substitutes models which assigned density and CT values are set up 3 cm under the water phantom surface at the center axis. A radiation field, 6 MV X-ray, 10 cm×10 cm, SSD=100 cm,is given to different models, then we extract the center axis depth dose which are used to compared with the one in pure water phantom.Results The dose curves in water phantom with air and lung appear second dose built-up effect below the inferior interface, and the rate of descend of the dose value is significantly slower then the one in pure water phantom. The depth dose values in the phantom included Muscle-Skeletal and Adipose-Tissue are mainly as same as the ones in pure water phantom, but the dose curve in Adipose-Tissue is slightly on top of the curve in pure water phantom; The depth of dose curves in Bone and AL model below the superior interface appear the second dose built-up effect, but the rate of descend of the dose value in them decreases rapidly below the inferior interface. All the curves tend to be parallel to the one in pure water phantom after a certain depth.Conclusion The second dose built-up effect will appear when X-ray passes through from low density substance to high density substance, and the greater of the density difference, the more obvious of the effect. The depth dose decreases rapidly when the X-ray passes through from high density substance to low density substance, and the greater density difference will lead to more obvious phenomenon. The depth dose characters can be useful in TPS planning design.
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Received: 15 June 2018
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