The influence of patient centering on CT dose and image noise
The influence of patient centering on CT dose and image noise
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DOI：
10.1118/1.2748113
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发表时间：
2007-07-01
期刊：
影响因子：
3.8
通讯作者：
Daly, Michael P.
中科院分区：
文献类型：
--
作者：
Toth, Thomas;Ge, Zhanyu;Daly, Michael P.
尽管自最早的CT扫描仪型号引入以来，已使用X射线强度成形滤波器（蝴蝶结滤波器），但对剂量和噪声的临床意义尚未充分了解。为了实现预期的剂量和噪声优势，需要将患者置于扫描视野的中心。在这项研究中，我们探讨了在临床实践中以病人为中心的影响。我们在GE LightSpeed VCT扫描仪上使用每个可用的源过滤器扫描各种尺寸和形状的体模，体模中心位于旋转中心（等中心点）下方0、3和6 cm处。在大图像区域上沿着图像噪声测量表面剂量。表面剂量和噪声的回归模型作为体模尺寸和中心误差的函数生成。还开发了使用定位扫描投影射线照片（SPR）确定偏心量的方法。然后，这些模型被用来回顾性地评估273例成人身体患者的临床意义。当偏离中心3 cm和6 cm时，32 cm CTDI体模上的表面剂量增加了18%和41%，而图像噪声也增加了6%和22%。成人身体侦察SPR扫描的回顾性分析显示，46%的患者在高度上偏离中心20-60 mm，平均位置在旋转中心（等中心点）以下23 mm。分析表明，表面剂量惩罚高达140%，平均剂量惩罚为33%，假设管电流增加，以补偿由于偏心增加的噪声。如果在定位患者时小心操作，则可以在带有蝴蝶结滤波器的扫描仪上提高临床图像质量和剂量效率。自动提供患者特定的定心和扫描参数选择信息可以帮助技术人员改进工作流程，实现更一致的图像质量并降低患者剂量。(C)2007年美国医学物理学家协会。
Although x-ray intensity shaping filters (bowtie filters) have been used since the introduction of some of the earliest CT scanner models, the clinical implications on dose and noise are not well understood. To achieve the intended dose and noise advantage requires the patient to be centered in the scan field of view. In this study we explore the implications of patient centering in clinical practice. We scanned various size and shape phantoms on a GE LightSpeed VCT scanner using each available source filter with the phantom centers positioned at 0, 3, and 6 cm below the center of rotation (isocenter). Surface doses were measured along with image noise over a large image region. Regression models of surface dose and noise were generated as a function of phantom size and centering error. Methods were also developed to determine the amount of miscentering using a scout scan projection radiograph (SPR). These models were then used to retrospectively evaluate 273 adult body patients for clinical implications. When miscentered by 3 and 6 cm, the surface dose on a 32 cm CTDI phantom increased by 18% and 41% while image noise also increased by 6% and 22%. The retrospective analysis of adult body scout SPR scans shows that 46% of patients were miscentered in elevation by 20-60 mm with a mean position 23 mm below the center of rotation (isocenter). The analysis indicated a surface dose penalty of up to 140% with a mean dose penalty of 33% assuming that tube current is increased to compensate for the increased noise due to miscentering. Clinical image quality and dose efficiency can be improved on scanners with bowtie filters if care is exercised when positioning patients. Automatically providing patient specific centering and scan parameter selection information can help the technologist improve workflow, achieve more consistent image quality and reduce patient dose. (C) 2007 American Association of Physicists in Medicine.