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<p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;"></span></strong></p><p style="text-align: center;"><img data-s="300,640" data-type="jpeg" src="http://mmbiz.qpic.cn/mmbiz_jpg/dx3KibwtDhveMrSJ5zQOrT5OlxfYs7IQCfhsPq1kmouTa4VBic1VJMlkmLdrv0xrMYSXS5U0gE2haLPb6qlD9Nzg/0?wx_fmt=jpeg" data-ratio="0.75" data-w="1280" /></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;"></span></strong><br /></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">随着CT设备普及和发展，正确的使用CT，减少球管的损耗，降低运行成本是</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">每个医院CT工作人员所关心的问题，下面本文从理论和实践两个方面就这个问</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">题进行一下探讨。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">一． X光成像原理：</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">1. X</span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">线之所以能使人体在荧光屏上或胶片上形成影像，一方面是基于X线的特性，即其穿透性、荧光效应和摄影效应；另一方面是基于人体组织有密度和厚度的差别。由于存在这种差别，当X线透过人体各种不同组织结构时，它被吸收的程度不同，所以达到荧光屏或X线片上的X线量即有差异。这样，在荧光屏或X线片上就形成 黑白对比不同的影像。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">因此，X线影像的形成，应具备以下三个基本条件：首先，X线应具有一定的穿透力，这 样才能穿透被照射的组织结构，第二，被穿透的组织结构，必须存在着密度和厚度的差异，这样，在穿透过程中校吸收后剩余下来的X线量，才会是有差别的；第 三，这个有差别的剩余X线，仍是不可见的，还必须经过显像这一过程，例如经X光照片或影像增强器显像，也可以采用探测器矩阵方式采集，进行A/D模数转换后形成数字图像，用显示器显示或用各种不同的打印机打印到不同的媒体上，才能显示出具有黑白对比和层次的X线影像。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">X</span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">线穿透密度不同的组织时，密度高的组织被吸收的多，密度低的组织被吸收的少，因而剩余的X线量就出现差别，从而形成黑白对比的X线影像</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">X</span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">线穿透厚度不同的组织或器官时，厚的部分吸收X线多，薄的部分</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">吸收X线少，因而剩余的X线量就出现差别</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">事实上、密度和厚度这两个因素经常是综合地影响X线成像。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;"><br /></span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">2. </span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">球管参数对成像的影响</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">影响X光成像质量的指标，我们一般主要用两个指标衡量，空间分辨率和密度分辨率，除去设备的原因以外，而球管的参数和性能也会对这两个参数产生重要的影响，下面我们从球管的角度分别对X光成像质量进行分析。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">A</span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">． 空间分辨率：</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">由于X射线实际上是一种波长极短的电磁波也是一种光，它除了具有穿透性及对生命体的生物效应等特性以外，也具备着光的一切特性，发光光源面积的大小直接影响成像的空间分辨率，这主要是由于光源的半影效应特性引 起的，所说的半影效应是指发光光源与被投影物体的成像关系，当光源几何尺寸大于被投影物体时，光源边缘的光线会通过被投影物体的边缘在投影影像上产生交汇，会使影像缩小或消失，手术室中的无影灯就是通过这种原理制成的。在X光影像设备中，要获得清晰的细微组织影像，从球管方面需要小的焦点，同时做投影时的操作也十分重要，所以在普通X光照相和透视时，人体距离球管越远，离影像增强器或照相胶片越近，所获得的影像越清晰。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">在CT中影响空间分辨率的因素很多，球管的焦点尺寸对CT的空间分辨率会产生一定的影响，而CT自身的因素如探测器的尺寸、数量、灵敏度，DAS数据采集通道的开关特性，球管安装校正精度，机器校正参数表格 的制作质量等都会对空间分辨率产生影响。球管的老化，靶面烧伤造成的散焦，球管旋转阳极轴承磨损造成的轴向和径向间隙过大引起的串动等都会形成球管等效焦点变大，球管内管芯松动产生的焦点偏移等，都会造成空间分辨率的降低。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">B.</span></strong><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">密度分辨率：</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">密度分辨率是指在或得的图像上面能够分辨出的最小组织密度差别，高的密度分辨率能够使我们在阅片时能够更清晰的看到组织内部的密度改变，提高诊断的准确性。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; text-indent: 32px; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">影响密度分辨率的因素较多，在CT本身方面，探测器灵敏度，数据采集部分的线性度，数模A/D转换器的位数，都会对密度分辨率产生影响，数模转换器的位数越多，每个转换台阶的最小值越小，密度分辨率就会越高。</span></strong></p><p style="max-width: 100%; min-height: 1em; color: rgb(62, 62, 62); font-family: 'Hiragino Sans GB', 'Microsoft YaHei', Arial, sans-serif; font-size: 16px; line-height: 25.6px; white-space: normal; box-sizing: border-box !important; word-wrap: break-word !important; background-color: rgb(255, 255, 255);"><strong style="max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;"><span style="max-width: 100%; font-family: 宋体; box-sizing: border-box !important; word-wrap: break-word !important;">在球管方面，要求球管所发出的X射线具有一定的频谱宽 度，线质较硬部分可以穿透骨骼等密度较大的组织，形成骨骼影像，线质较软的部分可以穿透软组织部分，形成组织影像。由于球管的长期使用，球管的靶面在电子的长时间轰击下，由于球管内部不是绝对真空，球管内的被电离的气体离子在高压电场作用下轰击到靶面上，造成靶面材质的改变，使球管发出的X射线线质发生改 变，线质变硬，软线部分减少。球管使用时间长或球管在使用中出现过热，球管散热不良等原因，使球管管芯的玻壳及出线窗口上结有积炭，在油中产生游离炭，使球管内冷却油的颜色变黑，造成X线光谱中波长较长的软线部分被炭吸收较多，而波长较短的硬线部分吸收较少，使得输出的X光线质变硬。积炭的对X射线线质的 影响要比球管自身老化影响大的多。由于硬线对软组织穿透能力较强，软组织对X线的硬线吸收能力很低，使软组织的密度分辨率下降。</span></strong></p><p><br /></p>
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发表于 2020-10-19 23:31:05