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KMID : 1164220170290020109
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Journal of Korean Society for Radiotherapeutic Technology
2017 Volume.29 No. 2 p.109 ~ p.117
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Evaluate the Change of Body Shape and the Patient Alignment State During Image-Guided Volumetric Modulated Arc Therapy in Head and Neck Cancer Patients
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Seo Se-Jeong
Kim Tae-Woo
Choi Min-Ho
Sohn Jong-Gi
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Abstract
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Objectives: The purpose of this study was to evaluate the change of body shape and the patient alignment state during image-guided volumetric modulated arc therapy in head and neck cancer patients,
Materials and Methods: We performed a image-guided volumetric modulated arc therapy plan for 89 patients with head and neck cancer who underwent curative radiotherapy. Ten of them were evaluated for set up error. The landmarks of the ramus, chin, posterior neck, and clavicle were specified using ARIA software (Offline review), and the positional difference was analyzed.
Results: The re-CT simulation therapy was performed in 60 men with 17±4 cycles of treatment. The weight loss rate was -6.47±3.5 %. 29 women performed re-CT simulation at 17±5 cycles As a result, weight loss rate was -5.73±2.7 %.
The distance from skin to C1, C3, and C5 was measured, an d both clavicle levels were observed to measure the skin shrinkage changes. The skin shrinkage standard deviations were C1 (± 0.44 cm), C3 (± 0.83 cm), and C5 (± 1.35 cm), which is about 1 mm shrinkage per 0.5 kg reduction. Skin shrinkage according to the number of treatments was 1 ~ 4 fractions (no change), 5 ~ 13 fractions (-2 mm), 14 ~ 22 fractions (-4 mm) and 23 ~ 30 fractions (-6 mm).
Conclusion: When the body shape changes about 5 mm, the central dose starts to differ about 3 % or more. Therefore, the CT simulation treatment for the adaptive therapy should be additionally performed. In addition, it is necessary to actively study the CT simulation therapy method and set up method of the lower neck and to examine the use of a new immobilization device.
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KEYWORD
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VMAT , IGRT , Skin shrinkage , Body shape change , Weight change
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