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KMID : 0948320040040010040
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Konyang Medical Journal
2004 Volume.4 No. 1 p.40 ~ p.43
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Comparison of Treatment Plan Regarding Lung-Equivalent Phantom
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Min Chul-Kee
Chung Weon-Kuu
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Abstract
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To produce a phantom that has the similar density of the human lung, and to compare the difference of absorbed in the target volume according to heterogeneity-corrected. The phantom that is a regular hexahedron made of PMMA, 303030 cm3. Inside the cube, there are 29291 cm3 cork plates stacked on top of each other. To compare the treatment plan for the actual lung density, a circular hole 25 cm in diameter has been made on four sides of the cube. SOMATOM PLUS4 (SIEMENS, Germany) CT has been used to scan the phantom under the following conditions: 5mm interval, 120 kV, 200 mA. Using the CT images along with PROWESS 3DTM(PROWESS, USA) system, we were able to draw virtual GTV, CTV, PTV, and when developing AP/PA and 3-D treatment plan, we compared and analyzed the maximum dose, minimum dose, target coverage through DVH of each according to heterogeneity-corrected. The results when comparing 2D and 3D plans according to heterogeneity-corrected, we can see a difference in maximum dose of 29.5%, 9.2%. When calculating without heterogeneity-corrected, the results showed that the isodose curve was distributed on the surface of the phantom in parallel-opposed direction. The results when analyzing the absorbed distribution of lung excluding GTV, according to heterogeneity-corrected, the difference between maximum dose and average dose was 27.7%, 8.3%, and dose was found to be distributed in greater numbers on Lung- equivalent Phantom when it dose not correct heterogeneity factor. When conducting 2D and 3D radiation therapy treatment plans using self-made Lung-Equivalent Phantom, there was 29.5% difference in maximum dose. This shows that when planning treatment for lungs that are composed of water and other atomic number, one should revise the heterogeneity-corrected factor.
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KEYWORD
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absorbed dose, radiation therapy planning, lung-equivalent phantom
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