| 医用CT仪上基于衰减的曝光量和峰值电压自动控制基本等式 |
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| 引用本文： | ZHENG Xiao-ming. 医用CT仪上基于衰减的曝光量和峰值电压自动控制基本等式[J]. CT理论与应用研究, 2016, 25(6): 625-632. DOI: 10.15953/j.1004-4140.2016.25.06.01 |
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| 作者姓名： | ZHENG Xiao-ming |
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| 作者单位： | Medical Radiation Science, School of Dentistry and Health Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia |
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| 摘 要： | 为了给患者以最少的辐射剂量而不影响诊断,现行医用CT仪都有基于噪声指标的自动曝光量控制。峰值电压对于图像质量和辐射剂量影响都很大,因此自动峰值电压控制很重要。本文从图像质量和辐射剂量优化的第一原理出发,给出基于衰减的曝光量和峰值电压同时自动控制的一般等式。此等式可用于单独曝光量自动控制或者单独峰值电压自动控制。对于单独暴光量自动控制,此等式要求对患者体厚度毎增加一厘米,曝光量要增加3.8%。对于单独峰值电压自动控制,此等式要求对患者体厚度每增加一厘米,峰值电压要平均增加1.53%。如果患者体厚度是常数,此等式要求平均百分比曝光量增加是百分比峰值电压减少的2.49倍。这些等式应该可以在现行医用CT仪上用于曝光量和峰值电压的自动控制。
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| 关 键 词： | 计算机断层成像 基本控制等式 自动曝光控制 自动峰值电压控制 X线衰减 |
| 收稿时间： | 2016-06-12 |
Attenuation Based Governing Equations for Automatic mAs and kVp Controls in Medical X-ray CT Imaging |
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| ZHENG Xiao-ming. Attenuation Based Governing Equations for Automatic mAs and kVp Controls in Medical X-ray CT Imaging[J]. CT Theory and Applications, 2016, 25(6): 625-632. DOI: 10.15953/j.1004-4140.2016.25.06.01 |
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| Authors: | ZHENG Xiao-ming |
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| Affiliation: | Medical Radiation Science, School of Dentistry and Health Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia |
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| Abstract: | Automatic exposure control based on noise index has been commonly implemented in current medical X-ray CT scanners in order to minimise radiation dose to patients while maintaining image quality for patient diagnosis. Automatic peak voltage control is also desirable as it is an important scanning parameter that has significant impact on both image quality and radiation dose. In this paper, a general attenuation based governing equation for simultaneous automatic controls of both mA s and kV p is presented which was derived from the first principle of radiation dose and image quality optimisation. This equation can be applied separately for automatic mA s control only or automatic kV p control only. The equation for automatic mA s control only states that the mA s should be increased by 3.8% for every 1cm increase of the patient body's sectional thickness if the peak voltage is kept constant. For automatic kV p control only, the equation states that the peak voltage should be increased by 1.53% percent on average for every 1 cm increase of the patient's body sizes if the mA s is kept as a constant. For a constant body thickness, the equation states that the average percentage mA s reduction should be 2.49 times the percentage peak voltage increase. The implementation of these equations in medical CT scanners has been described in a recent Australian patent. |
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| Keywords: | computed tomography governing equations automatic exposure control automatic peak voltage control X-ray attenuation |
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