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Year : 2014  |  Volume : 10  |  Issue : 4  |  Page : 932-936

A comparison between four immobilization systems for pelvic radiation therapy using CBCT and paired kilovoltage portals based image-guided radiotherapy

1 Department of Radiation Oncology, Fortis International Oncology Center, Noida, India
2 Department of Radiation Oncology, International Oncology Center, Fortis Hospital, Noida, National Capital Region, India
3 Department of Radiation Oncology, Max Cancer Center, Max Super Specialty Hospital, New Delhi, India
4 Max Hospital, Apothecaries Pvt. Limited, Patparhganj and Saket, New Delhi, India

Correspondence Address:
Gagan Saini
Department of Radiation Oncology, Fortis International Oncology Center, Sector - 62, Noida, National Capital Region
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0973-1482.138026

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Introduction: We commonly use 6- and 4-clamped thermoplastic molds (TMs) for rigid immobilization during pelvic radiotherapy (RT), sometimes a vacuum cushion (VC) is also used as leg support with TM. Our objective was to report the setup margins (SMs) associated with the different systems, to analyze whether any of these systems is superior, and to analyze whether any of them showed better reproducibility in any particular direction. Materials and Methods: Retrospective analysis was done by dividing the patients into four groups: 6-clamp with VC (6CVC), 6-clamp without VC (6CNC), 4-clamp with VC (4CVC), and 4-clamp without VC (4CNC). A repeat offline review was done for all patients and errors were tabulated. Statistical methods were then applied. Results: Total 24 patients had 413 image-guided RT (IGRT) sessions, 312 were cone beam computed tomography scan (CBCT) scans and 101 were paired kilovoltage portals (kVp). There was no statistically significant difference between 6CVC and 6CNC. However, while comparing 4CVC and 4CNC, a statistically significant difference was seen in all directions. VC improved precision in vertical and lateral direction mainly, while the 6-clamped TM improved reproducibility in longitudinal direction. Conclusions: SM was low for all the four immobilization systems studied. There is no added benefit of using a VC with 6-clamped TM for pelvic RT. Use of a VC is recommended with 4-clamped TM to improve overall reproducibility. 6-clamped TM helps keep the errors low.

Abstract in Chinese

使用CBCT盆腔放疗四制动系统和基于配对千伏门户图像引导放射治疗的比较 摘要 简介:我们通常使用6和4卡的热塑性塑料模具(TMS)在盆腔放疗(RT)中严格制动,有时真空垫(VC)加上TM也被用作支撑腿。我们的目标是报告不同系统相关的设置范围(SMs),分析哪个系统是否会更好,并分析它们在任何特定的方向上是否有更好的重复性。 材料与方法:将患者分为4组作回顾性分析:6夹带真空垫(6cvc),6夹不带真空垫(6cnc),4夹带真空垫(4cvc),4夹不带真空垫(4cnc)。对所有病人做了脱机重复性回顾,对误差列表。然后应用统计方法。 结果:共24例病人,413次图像引导放疗(IGRT),312次是锥形束计算机断层扫描(CBCT),101次是配对千伏门户(KVP)。6cnc和 6cvc之间没有统计上的显着差异。然而,当比较4cvc和4cnc时,在所有方向上看到的都有统计学差异。真空垫提高在垂直和横向方向为主的精度,而6卡模具模改进轴方向可重复性。 结论:所有研究的4制动系统中设置范围都是低的。使用真空垫加 6卡模具对盆腔放疗没有额外的好处。推荐使用真空垫加 4卡模具以提高全方位的重复性。6卡模具有助于保持低误差。 关键词:误差,图像引导放疗,膝盖休息,边缘,计划靶体积

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