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The Individual Setup Errors Correction Should Be Given for Patients with Tomotherapy

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Y Tong

Y Tong1,2*, G Gong1 , P Cheng2 , Y Yin1 , (1) Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong Province, China.(2) School of Nuclear Science and Technology, University of South China, Hengyang, Hunan Province,China.


SU-I-GPD-J-114 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To investigate the distribution rules of setup errors of different parts tumors for Tomotherapy.

Methods: 151 patients received Tomotherapy were retrospectively analyzed in this study, including 53 head and neck tumors, 45 thoracic tumors, 20 abdominal tumors, and 33 pelvic tumors. The planning CT images of patients were obtained, and all patients underwent Megavoltage CT (MVCT) scans before radiotherapy in each fraction. And the setup errors were recorded after rigid registering MVCT images to planning CT images, setup errors on ₊Χ(left), ₋Χ(right), ₊Υ(head), ₋Υ(foot), ₊Ζ(ventral), and ₋Ζ(dorsal)directions were analyzed respectively.

Results: 3281 MVCT scans were performed for 151 patients, the mean setup errors on six directions were less than 3 mm for head and neck tumors, and on ±Χ, ±Υ directions were less than 4 mm for thoracic, abdominal, and pelvic tumors, which were symmetrical on different directions of same axes. The distributions of setup errors on Ζ axes were asymmetrical, and the setup errors along the ₊Ζ direction were significantly higher than that along the ₋Ζ direction (P< 0.05). The mean setup errors on ₊Ζ and ₋Ζ were 3.24 mm and 1.75 mm, 6.71 mm and 2.64 mm, 6.74 mm and 1.92 mm, 7.18 mm and 1.92 mm for head and neck, thoracic, abdominal, and pelvic tumors. And the setup errors on ₊Ζ direction increased following the distance from tumors to head.

Conclusion: The setup of head and neck tumors has good repeatability for Tomotherapy; and the heterogeneity of setup errors on ventral- dorsal directions for all parts of tumors should not be ignored. It is necessary to undergo individual setup errors correction for patients who accept Tomotherapy.

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