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<section><section powered-by="gulangu"><section><section><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><strong><span>来源:</span></strong></p><p><strong><span><br /></span></strong></p><p>自1972年第一台EMI型头颅CT问世后,CT先后经历了五代结构性能的发展和改变。(北京纳米维景在RSNA2018上有首次展示其自主研发的第六代CT-静态CT,详情请戳看点剧透!这些“黑科技”即将在RSNA 2018首度“绽放”!)<br /></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><p><strong>第一代(平移+旋转扫描方式)</strong></p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/0e8917d8ed10cfa0bbfef7234c660d53_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>最早的第一代CT扫描机于1971年安装在winbledon医院。以后生产的一般都用Mark I 来表示。</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/a2add35fc763d7e1426c856731c8fcce_3.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><span>(EMI Mark I Head CT Scanner)</span></p><p><br /></p><p>这类扫描机多属于头部专用机。由一个X射线管和两个或三个晶体探测器组成。由于X射线束被准直成像铅笔芯粗细的线束,故又称为笔形扫描束装置。X射线管与探测器连成一体,X射线管产生的射线束和相对静止的探测器环绕人体的中心做同步直线平移扫描运动。穿过人体头部的线束被另一段的NaI晶体探测器接收。第一代CT,矩阵为80*80,共产生6400个显示单元(像素值)。</p><p><br /></p><p>在EMI型CT扫描机中,病人的头部被放置在一个圆形橡胶帽中。这样是为了确保X射线的路径穿病人的头部。</p><p><br /></p><p>第一代EMI型CT扫描机X射线利用率很低,扫描时间长,通常需要3~5分钟的时间,重建一幅图像的时间为5分钟。所以在做CT检查时,计算机上重建一幅图像的同时收集下一幅图像的数据。如果病人需要扫描6个层面,则需要35分钟的时间。第一代扫描机基本能够满足人体头部的扫描图像。然而,由于扫描时间比较长,很难抑制图像的运动伪影,尤其是在扫描腹部时,运动伪影极其严重。因此第一代扫描机首先需要改进的是扫描时间长的问题,于是产生了第二代CT扫描机。</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><p><strong>第二代(平移+旋转扫描方式)</strong></p></section></section></section></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/835ae0e6b4565b8c45572e63f17e6389_4.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>第二代CT机与第一代CT机的明显区别在于把第一代单一笔形X射线束改为扇形线束,探测器数目也增加到3~30个。每次扫描后的旋转角由1度提高到3度~30度。这样旋转180度时,扫描时间就缩短到20~90秒。但这个时间对于扫描腹部器官来说仍然不能避免运动伪影的产生。由于探测器数目增加,就用连续扇形X线束替代了每个笔形X射线束。扇形线束可以照射到更大的提及范围,但同时也产生了更多的散射线。此外,每个探测器的性能和灵敏度必须一致。由于第二代CT机的X射线源和探测器之间的每束X射线没有分别被准直,结果使投向病人的部分射线中照射在探测器的间隔中而没有得到有效地利用</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><p><strong>第三代(旋转-旋转扫描方式)</strong></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>第一代和第二代都是采用平移+旋转运动,这种运动方式限制了扫描速度的进一步提高。为了减少运动时间而取消平移运动,使得X射线管和探测器作为整体之围绕病人做旋转运动而进一步缩短了扫描时间。1975年,美国GE公司首先推出了这种方式的CT机。称为第三代CT扫描机。</p><p><br /></p><p>第三代CT机有较宽的扇形角(30度~45度),可以包括整个被扫描体的截面,探测器的数目也极大地增加了。第三代CT扫描机的扫描时间在投放市场初期就已经缩短到20秒。使得在一次屏气时间内扫描一幅完整的图像的目标得以实现。</p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/ec29cb0892057f5f346bd990b5dc8a38_5.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p>第三代CT机的几何结构也与第一代、第二代CT有若干原则区别,因为扇形角宽(扇形角为30度~45度),像第一代、第二代CT那样安置X射线管就不可能了(由于旋转阳极小)。因此X射线管必须环绕其中心线转过90度。这样一来就不允许有直线形焦点。小焦点的另一个优点是产生的伪影少,提高了剂量效率和图像质量。</p><p><br /></p><p>第三代CT所要求的技术性较高,但在成本和图像质量方面具有较大的优势。第三代CT的扫描时间现在已可达到0.5秒以内,是目前临床上应用最为广泛的一种CT机。</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><p><strong>第四代(旋转-静止)</strong></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><img src="image/20201014/6938c3a0da39134a27a2b9bc7f52b4aa_6.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>1976年,美国科学工程(AS&E)公司首先推出了第四代CT扫描机,它用600个探测器排成圆周。扫描方式是探测器静止而只有X射线管旋转。扇形线束角度也较大,单幅的数据获取时间缩短。第四代CT扫描机的缺点是对散射线极其敏感,因此在每只探测器旁加一小块翼片做准直器。但这却浪费了空间,增加了病人所受的辐射剂量。第四代扫描机探测器数量最多可达72000个,这就加大了设备的成本,并且这么多的额探测器在扫描过程中并没有充分利用,因此第四代CT扫描机与第三代CT扫描机相比已没有明显的优势了。所以只有极少数厂家生产第四代CT扫描机。<br /></p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/b5cea16b86f03dca6b862a3c35a1ac51_7.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p>(PICKER 第四代全身螺旋CT)</p><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201014/53abde2b50d118ac9a207c0fc2fab536_8.png" /></p></section></section></section><section powered-by="gulangu"><section><section><p><span>(TOSHIBA TCT-TCT-400S CT Scanner)</span><br /></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><p><strong>第五代:静止-静止方式</strong></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><section></section><section></section><section><section><p><strong>电子束CT</strong></p></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>第一台电子束CT由D.P Body开发,并由Imatron公司推向市场,然而目前用于临床上的数量并不多。电子束CT(EBT,EBCT),通常又称为电影CT,或超高速CT(UFCT),主要应用于心脏的扫描。</p><p><br /></p><p><p><img src="image/20201014/55ebd67ae3e2a1c18f011a556d69cca2_9.png" /></p></p><p><br /></p><p>但电子束CT在心脏成像方面的垄断地位受到了多层螺旋CT的挑战。已证实具有亚秒级扫描时间和多层螺旋能力的普通CT也可以获得较高质量的心脏图像。关于多层螺旋CT可以看为什么多层螺旋CT能风靡世界20年?和同为64排CT,为什么“它”叫128层,“你”却是64层?</p></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><section></section><section></section><section><section><p><strong>动态空间再现机</strong><br /></p></section></section></section></section></section><section powered-by="gulangu"><section><section><p><br /></p></section></section></section><section powered-by="gulangu"><section><section><p>第五代CT机的另一种形式是“动态空间再现机”,它利用普通 CT技术实现快速容积扫描。设计者R.A.Robb计划用28个X线球管和28个荧光屏围绕着病人连续旋转。与连续单层扫描不同,它采用锥形束只在一圈旋转扫描中就覆盖整个容积。美国梅奥诊所有安装一台<span>仅用14个球管的,</span>动态空间再现机的缩小版。它重大数吨,可同时采集240层0.9mm厚的层面,总扫描时间只有1秒,用于动物生理学实验。因其体积巨大,也被称为“梅奥巨人”。</p></section></section></section></section><p><br /></p><p><strong><span>本文由整理/原创,转载请注明出处。</span></strong></p><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>未来十年CT技术的发展方向</span><br /></p><p><br /></p><p><span>CT球管的前世今生!</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></section></section></section></section></section></section></section></section></section></section></section><p><br /></p><p><span><strong><span><p><img src="image/20201014/225eae26a91575de7508aebe3e999278_11.jpg" /></p></span></strong></span></p>
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