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<section data-role="paragraph" data-color="rgb(182, 228, 253)" data-custom="rgb(182, 228, 253)"><section><section><section><section powered-by="gulangu"><section><section><section><section powered-by="gulangu"><section><section><section><section powered-by="gulangu"><section><section><section><section powered-by="gulangu"><section><section><section><section><p><p><img src="image/20201014/86b79d371e9862b01189f0252a03b2cd_1.png" /></p></p></section><section><section><span><strong></strong></span></section><p><span>医疗器械媒体报道先锋</span></p><p><span>分享专业医疗器械知识</span></p></section><section><section><section>关注</section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section></section><p><span><strong><span>来源:</span></strong></span></p><p><span><strong><span><br /></span></strong></span></p><section><section powered-by="gulangu"><section><section><p>我们在面包店常常能看到切好的吐司面包，抹上黄油或加上奶酪用平底锅烤热就是完美的早餐。可你有没有想过，这常见的吐司面包中蕴含着CT成像的基本原理？<br /></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/0db05de92c18ce24fe6f779679a76ea9_2.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>X射线计算机体层摄影（X-ray computed tomography, CT ）又称“计算机体层摄影”，就是利用X射线对人体进行一层一层的断层扫描，再根据人体内各种组织对X射线的吸收差异，即测定X射线在人体内的衰减系数为基础，采用一定的数学方法，经过计算机处理，得出该层面内的衰减系数值在人体内的二维分布矩阵，并转变为图像湖面上的灰度分布，从而实现建立断层图像的现代医学成像技术。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/e63f779ad01e464749275321ff53e1a9_3.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><svg xmlns="http://www.w3.org/2000/svg" x="0px" y="0px" viewbox="0 0 64.7 40.8" width="100%"><g><path d="M36.2,27c0,0.2,0,0.4,0,0.6l0,0c0.5,7.4,6.7,13.3,14.2,13.3c7.9,0,14.3-6.4,14.3-14.3c0-7.2-5.3-13.1-12.2-14.1 C53,8.9,54.2,4,57,0c0,0-19,3-20.7,24.7c-0.1,0.6-0.1,1.2-0.1,1.8C36.2,26.7,36.2,26.9,36.2,27z" fill="rgb(144,201,224)"></path><path d="M0,27c0,0.2,0,0.4,0,0.6l0,0C0.6,35,6.7,40.8,14.3,40.8c7.9,0,14.3-6.4,14.3-14.3c0-7.2-5.3-13.1-12.2-14.1 C16.8,8.9,18,4,20.8,0c0,0-19,3-20.7,24.7C0,25.3,0,26,0,26.6C0,26.7,0,26.9,0,27z" fill="rgb(144,201,224)"></path></g></svg></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><strong>CT的历史<br /></strong></p></section></section></section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><svg xmlns="http://www.w3.org/2000/svg" x="0px" y="0px" viewbox="0 0 64.7 40.8" width="100%"><g><path d="M28.5,13.8c0-0.2,0-0.4,0-0.6l0,0C28,5.8,21.8,0,14.3,0C6.4,0,0,6.4,0,14.3c0,7.2,5.3,13.1,12.2,14.1 c-0.5,3.5-1.7,8.4-4.5,12.5c0,0,19-3,20.7-24.7c0.1-0.6,0.1-1.2,0.1-1.8C28.5,14.1,28.5,14,28.5,13.8z" fill="rgb(144,201,224)"></path><path d="M64.7,13.8c0-0.2,0-0.4,0-0.6l0,0C64.2,5.8,58,0,50.5,0c-7.9,0-14.3,6.4-14.3,14.3c0,7.2,5.3,13.1,12.2,14.1 c-0.5,3.5-1.7,8.4-4.5,12.5c0,0,19-3,20.7-24.7c0.1-0.6,0.1-1.2,0.1-1.8C64.7,14.1,64.7,14,64.7,13.8z" fill="rgb(144,201,224)"></path></g></svg></section></section></section></section></section></section></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><span>1895年，德国物理学家伦琴发现了X射线。这是人们第一次透过皮肤看到体内骨骼，由此形成了新的学科——放射诊断学，并奠定了医学影像学的基础。</span><br /></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/bd6be5d042c3dadd591ca76b814f1d60_4.jpg" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p>常规X射线摄影以及后来出现的各种数字化X射线成像技术，是人体三维结构的二维重叠显示，会造成人体内部组织影像互相重叠，不易分辨出病灶的确切位置和细节。此外，常规X射线摄影对于吸收系数很接近的组织如肝脏、胰腺中的病变难以区分，这些部位在临床上被视为常规X射线诊断的盲区。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/c52a0ad66094a62a181f2158e9ed66ea_5.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p>1914年，俄国学者K.maenep依照运动产生模糊的理论，首先提出体层摄影的理论。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/f2e1aca1696d0edb68d01f8aeb276f71_6.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p><span>1917年，奥地利数学家Radon提出了图像重建理论的数学方法。</span><br /></p><p><br /></p><p>1930年意大利的Vallebona开始将体层摄影的有关理论和它的使用方法应用于临床并取得了很好的临床效果，1947年率先取得了以人体为模型的横断面影像。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/f95b3957091ba85287a4e73acada5dfb_7.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p>1961年美国神经内科医生Oldendorf根据“旋转-平移”实验提出了电子计算机X射线体层技术的理论。</p><p><br /></p><p>美国物理学家A.M.Cormack发明了简单的CT模拟装置。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/9b9336c94789ea9f2645fb4b4be19b9f_8.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p>1968年英国工程师Hounsfild与神经放射学Ambrose共同协作设计，于1972年由英国EMI公司制造了用于头部扫描的电子计算机X射线体层装置并在英国放射学会学术会议山公之于世，称EMI扫描仪。</p><p><br /></p><p>1974年在Montreal召开的第一次国际专题讨论会上正式将这种检查方法称作电子计算机体层摄影（computed tomography,CT）。</p><p><br /></p><p><p><img src="image/20201014/02d35380e8e6e209f97db9f73fd805de_9.png" /></p></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p>CT的发明被认为是自1895年伦琴发现X射线以来，在放射医学、医学物理和相关学科领域里，最伟大的发明。为此，Hounsfield和Cormack获得了1979年的诺贝尔生理学或医学奖。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><svg xmlns="http://www.w3.org/2000/svg" x="0px" y="0px" viewbox="0 0 64.7 40.8" width="100%"><g><path d="M36.2,27c0,0.2,0,0.4,0,0.6l0,0c0.5,7.4,6.7,13.3,14.2,13.3c7.9,0,14.3-6.4,14.3-14.3c0-7.2-5.3-13.1-12.2-14.1 C53,8.9,54.2,4,57,0c0,0-19,3-20.7,24.7c-0.1,0.6-0.1,1.2-0.1,1.8C36.2,26.7,36.2,26.9,36.2,27z" fill="rgb(144,201,224)"></path><path d="M0,27c0,0.2,0,0.4,0,0.6l0,0C0.6,35,6.7,40.8,14.3,40.8c7.9,0,14.3-6.4,14.3-14.3c0-7.2-5.3-13.1-12.2-14.1 C16.8,8.9,18,4,20.8,0c0,0-19,3-20.7,24.7C0,25.3,0,26,0,26.6C0,26.7,0,26.9,0,27z" fill="rgb(144,201,224)"></path></g></svg></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><strong>CT成像基本原理</strong></p></section></section></section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><svg xmlns="http://www.w3.org/2000/svg" x="0px" y="0px" viewbox="0 0 64.7 40.8" width="100%"><g><path d="M28.5,13.8c0-0.2,0-0.4,0-0.6l0,0C28,5.8,21.8,0,14.3,0C6.4,0,0,6.4,0,14.3c0,7.2,5.3,13.1,12.2,14.1 c-0.5,3.5-1.7,8.4-4.5,12.5c0,0,19-3,20.7-24.7c0.1-0.6,0.1-1.2,0.1-1.8C28.5,14.1,28.5,14,28.5,13.8z" fill="rgb(144,201,224)"></path><path d="M64.7,13.8c0-0.2,0-0.4,0-0.6l0,0C64.2,5.8,58,0,50.5,0c-7.9,0-14.3,6.4-14.3,14.3c0,7.2,5.3,13.1,12.2,14.1 c-0.5,3.5-1.7,8.4-4.5,12.5c0,0,19-3,20.7-24.7c0.1-0.6,0.1-1.2,0.1-1.8C64.7,14.1,64.7,14,64.7,13.8z" fill="rgb(144,201,224)"></path></g></svg></section></section></section></section></section></section></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p><strong>CT成像的几个基本概念</strong></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><span><p>体层</p></span></section><section><section powered-by="gulangu"><section><section><p>指受检体中的一个薄层，又称之为断层，此断层的两个表面可粗略视为平行的平面。CT建立一幅图像的扫描过程中，受检体中被X射线束投射的部分就是此断层。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>像素</p></span></section><section><section powered-by="gulangu"><section><section><p>构成图像的基本单元。是具有一定分辨能力的感光点。对于二维图像来说，像素就是图像平面的面积元，按一定的大小和一定的坐标人为地划分。图像划分的像素数越多，像素就越小，画面就越清晰，携带的生物信息量就越大。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>体素</p></span></section><section><section powered-by="gulangu"><section><section><p>指在扫描野中按照一定的大小和一定的坐标人为划分的小体积元。对划分好的体素进行空间的编码，即形成对编好序号的体素阵列。划分的方案有多种，如256*256、320*320、512*512</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>线性衰减系数</p></span></section><section><section powered-by="gulangu"><section><section><p>CT本质上是一种利用X射线穿透人体后的衰减特性作为诊断依据的成像装置。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>CT值</p></span></section><section><section powered-by="gulangu"><section><section><p>相对于水的衰减计算出来的衰减系数称为CT值。为了纪念CT的发明者，将CT值的单位指定为Hounsfield单位（HU）。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>图像重建</p></span></section><section><section powered-by="gulangu"><section><section><p>CT中将采集的各个剖面数据（也叫原始数据）通过计算机计算获得图像的过程叫图像重建。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p><p><strong><span><br /></span></strong></p><p><strong><span>CT技术和指标</span><br /></strong></p><p><strong><span><span></span></span></strong></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><span><p>窗宽和窗位</p></span></section><section><section powered-by="gulangu"><section><section><p>CT图像的像素值范围为4096，所以可以显示4096个灰度级，但是人眼最多只能识别64个灰度级。所以在图像显示时，一般只显示感兴趣的一段CT值，这段CT值范围叫窗宽，其中心位置的值叫窗位。大于窗宽的CT值在显示时都为白色，小于窗宽的CT值显示为黑色。通过调节窗宽和窗位可以使图像显示出不同的细节，有利于图像的诊断。CT中的这种图像显示技术称为窗口技术。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>空间分辨率</p></span></section><section><section powered-by="gulangu"><section><section><p>也叫高对比度分辨率，是指图像中对比度最大（CT值最大和最小）的两点之间的分辨能力，即CT对空间两点的辨别能力，常用mm或线对数/cm表示。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>密度分辨率</p></span></section><section><section powered-by="gulangu"><section><section><p>低对比度分辨率。是指分辨对比度较小（CT值之差下小于10HU）的物体微小差别的能力，也即描述不同人体组织物理密度的微小差别的能力。常用百分单位表示，通常CT机的密度分辨率为0.3%～2%/平方厘米</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>伪影</p></span></section><section><section powered-by="gulangu"><section><section><p>在图像中存在，但在实际物体中并不存在的那部分图像；CT图像中，伪影的出现可以表现为一个虚假结构（像混杂伪影、线束硬化伪影、运动伪影和局部容积伪影）或CT值错误。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><span></span><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><strong>CT主要技术指标</strong><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><span><p>扫描时间</p></span></section><section><section powered-by="gulangu"><section><section><p>指完成一次数据采集X射线穿透人体所持续的时间；螺旋CT的扫描时间指限定扫描架旋转360度的时间。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>扫描方式</p></span></section><section><section powered-by="gulangu"><section><section><p>指球管和探测器的运动方式。螺旋CT属于螺旋扫描方式，有低压滑环和高压滑环之分。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>断层厚度</p></span></section><section><section powered-by="gulangu"><section><section><p>指扫描切片的厚度，有0.5mm、1mm、2mm、5mm、10mm之分。在扫描时可以选择。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>重建时间</p></span></section><section><section powered-by="gulangu"><section><section><p>在主计算机的控制下，将原始数据重建成显示图像的数据矩阵所需要的时间。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>重建矩阵</p></span></section><section><section powered-by="gulangu"><section><section><p>指将原始数据计算出的CT图像的矩阵大小。早期有256*256，现在常为512*512，高的又怒1024*1024</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><span><p>探测器数目</p></span></section><section><section powered-by="gulangu"><section><section><p>第三代阵列探测器或第四代环形探测器的数目。</p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>CT对脑部、颈部、纵隔、肺、胸壁、经皮穿刺检查、大血管、脊椎、后腹膜、肝、脾、肾、胰、肾上腺、子宫、卵巢、膀胱、异物等软组织病变、侵犯程度以及病变位置的确认有很好的临床应用价值。CT不仅对疾病的诊断有帮助，还有助于疾病的治疗计划的实施，特别是放射治疗计划的制订。<br /></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>CT发展史为系列文章，更多精彩敬请期待后续更新～</p><p><br /></p></section></section></section></section><section data-role="outer" label="Powered by gulangu"><section data-role="paragraph" data-color="#374aae"><p><strong><span>本文由翻译/整理，转载请注明出处。</span></strong></p></section></section><section data-role="outer" label="Powered by gulangu"><p> </p><section data-id="1658"><section><section><section data-id="1658"><section><section><section data-id="1658"><section><section><section data-id="1658"><section><section><p><span><strong>相关阅读</strong></span></p></section><p><p><img src="image/20201014/ec237188ae1e9c03eb4d9814f31b18ab_10.gif" /></p></p><p><br /></p><p><span>如何花最少的钱造一台CT？</span><br /></p><p><br /></p><p><span>同为64排CT，为什么“它”叫128层，“你”却是64层？</span><br /></p><p><br /></p><p><span>科普动画|MRI、CT、PET分别是怎么扫描图像的？</span><br /></p><p><br /></p><p><span>为什么多层螺旋CT能风靡世界20年？</span><br 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发表于 2020-10-14 14:56:01