Evaluating the four-dimensional cone beam computed tomography with varying gantry rotation speed
Evaluating the four-dimensional cone beam computed tomography with varying gantry rotation speed
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DOI：
10.1259/bjr.20150870
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发表时间：
2016-01-01
影响因子：
2.6
通讯作者：
Kumar, Shaleen
中科院分区：
文献类型：
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作者：
Yoganathan, S. A.;Maria, K. J.;Kumar, Shaleen
目的：评价不同机架转速下四维锥束CT （4DCBCT）的成像效果。方法：所有4DCBCT图像采集均在Elekta XVI Symmetry （TM）系统（Elekta AB, Stockholm, Sweden）中进行。一个具有直径1、2和3厘米的肿瘤模拟插入的动态胸腔假体被编程来模拟目标的呼吸运动（4秒）。在不同的龙门旋转速度（36度、50度、75度、100度、150度和200度min(-1)）下获取4DCBCT图像。由于4DCBCT系统的技术限制，利用4DCBCT的10个相位得到的平均锥束CT （CBCT）图像进行内部目标体积（ITV）轮廓。将平均CBCT与四维CT （4DCT）的ITVs进行比较。此外，还使用Catphan (R) 600 （the Phantom Laboratory Inc., Salem， NY）对不同龙门旋转速度下的4DCBCT图像质量进行了评估。结果：与4DCT相比，CBCT平均低估了ITV。ITV偏差随着龙门速度的增加而增加（36度和200度min（-1）为3 cm目标时为210.8% vs 217.8%）和目标尺寸的减小（目标直径为3和1 cm为200度min（-1）为217.8% vs 226.8%）。同样，空间分辨率、噪比、均匀性等图像质量指标也随着龙门转速的增加而下降。结论：采用4DCBCT对ITV进行定位时，应考虑龙门旋转速度的影响。幻像研究表明，慢速龙门旋转的4DCBCT图像质量更好，ITV偏差较小。知识进步：通常Elekta 4DCBCT系统的龙门架旋转周期恒定在4min（50°min(-1)）进行采集，任何减少/增加采集时间的尝试都需要仔细研究。本研究对不同龙门旋转速度下的4DCBCT图像进行了评价。
Objective: The purpose of this work was to evaluate the four-dimensional cone beam CT (4DCBCT) imaging with different gantry rotation speed.Methods: All the 4DCBCT image acquisitions were carried out in Elekta XVI Symmetry (TM) system (Elekta AB, Stockholm, Sweden). A dynamic thorax phantom with tumour mimicking inserts of diameter 1, 2 and 3 cm was programmed to simulate the respiratory motion (4 s) of the target. 4DCBCT images were acquired with different gantry rotation speeds (36 degrees, 50 degrees, 75 degrees, 100 degrees, 150 degrees and 200 degrees min(-1)). Owing to the technical limitation of 4DCBCT system, average cone beam CT (CBCT) images derived from the 10 phases of 4DCBCT were used for the internal target volume (ITV) contouring. ITVs obtained from average CBCT were compared with the four-dimensional CT (4DCT). In addition, the image quality of 4DCBCT was also evaluated for various gantry rotation speeds using Catphan (R) 600 (The Phantom Laboratory Inc., Salem, NY).Results: Compared to 4DCT, the average CBCT underestimated the ITV. The ITV deviation increased with increasing gantry speed (210.8% vs 217.8% for 36 degrees and 200 degrees min(-1) in 3-cm target) and decreasing target size (217.8% vs 226.8% for target diameter 3 and 1 cm in 200 degrees min(-1)). Similarly, the image quality indicators such as spatial resolution, contrast-to-noise ratio and uniformity also degraded with increasing gantry rotation speed.Conclusion: The impact of gantry rotation speed has to be considered when using 4DCBCT for ITV definition. The phantom study demonstrated that 4DCBCT with slow gantry rotation showed better image quality and less ITV deviation.Advances in knowledge: Usually, the gantry rotation period of Elekta 4DCBCT system is kept constant at 4min (50 degrees min(-1)) for acquisition, and any attempt of decreasing/increasing the acquisition duration requires careful investigation. In this study, the 4DCBCT images with different gantry rotation speed were evaluated.