彩超基本参数简介

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                    <section><section powered-by="gulangu"><section><p><img src="image/20201019/a7a8e460aaa94e8c65568e89538b9ff0_1.gif" /></p></section></section><section powered-by="gulangu"><section><section><p>扫描和时间</p></section><p><img src="image/20201019/2d6679eee67edf391cecc54a9b74e9fe_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; 沿着不同方向超声系统发射接收超声波形形成断层图像。探头阵子不能同时接收发送信号，超声波发射、接收交替工作，交替的频率就叫做脉冲重复频率。扫描图像的时间与之密不可分。</p></section></section></section><section powered-by="gulangu"><section><section><p>扫查线数</p></section><p><img src="image/20201019/2d6679eee67edf391cecc54a9b74e9fe_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; 单点聚焦情况下，形成一幅图像发送接收信号的次数。在超声诊断装置中，形成断层图像大约需要300条扫查线。</p></section></section></section><section powered-by="gulangu"><section><section><p>脉冲重复频率PRF</p></section><p><img src="image/20201019/2d6679eee67edf391cecc54a9b74e9fe_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;脉冲重复频率PRF：1秒钟发射接收信号的次数，它对成像时间有很深的影响。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; 深部反射，接收信号需要时间长，也就是发出脉冲信号的时间间隔也会长，换句话就是说PRF低；如果扫查的深度小，接收信号需要时间短，PRF高。</p><p>例如：PRF为3.7KHZ的时候，往返周期由以下公式可以得到：1/3700HZ=270μs，超声波在人体内1cm往返约13μs，所能扫查视野深度值为270μs/13μs=21cm，所以扫描中要计算出适应不同视野深度的PRF值。</p></section></section></section><section powered-by="gulangu"><section><section><p>帧频率</p></section><p><img src="image/20201019/2d6679eee67edf391cecc54a9b74e9fe_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 帧频率：1秒钟扫描出几幅图像为振频率。例如：扫查线数为N=121条，扫查深度D=20cm，一帧扫描图像所需的时间T=N*2D/C=121*2*20cm/1530*100（cm/s）=31.6（ms）；2D/C=1/PRF：往返周期。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;1秒钟扫描出的帧频数为R，R=1/T=1s/31.6,ms=31.6帧</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;这说明帧频与所扫查的深度成反比的关系，即：扫查深度大，帧频低，反之则反。</p></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; 对于帧频的影响与很多因素有关；如果扫描线减少的话，帧频变高。</p><p>&nbsp; &nbsp; &nbsp; &nbsp;帧频高有两种方法：一种是扫查线密度低，另一种是扫查深度小。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; 决定帧频的因素：扫查线密度、视野角度、扫查深度。</p></section></section></section><section powered-by="gulangu"><section><section><p>分辨力</p></section><p><img src="image/20201019/2d6679eee67edf391cecc54a9b74e9fe_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;超声波诊断仪是用识别两点之间的最小距离的能力来表示分辨力。<br  /></p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;距离分辨力有两种，一种是纵向分辨力、一种是横向分辨力、一种是侧向分辨力。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;纵向分辨力，有名纵向分辨力，即与声束方向相同的相邻两点之间的识别能力。纵向分辨力由脉冲长度决定，脉冲长度越小，纵向分辨力越大（等同波数时频率越高分辨力越高）。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 横向分辨力（Transverse Resolution）:与声束方向垂直相邻两点的识别能力。为了提高横向分辨力，可以细化声束，也可调整聚焦。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 侧向分辨力（Lateral Resolution）:垂直于二维扫查切面的相邻两点的识别能力。超声扫查切面具有一定的厚度，这个厚度范围的所以信息（相当于多个二维切面信息）最终显示为一个二维平面上，导致伪像，叫做容积伪像。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;描述超声成像灵敏度的两个重要参数：对比分辨率与细微分辨率。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;对比分辨率：超声诊断仪能够显示出最小声阻抗差值的能力。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;细微分辨率：超声诊断仪能够显示出最小背向散射信号的能力。</p></section></section></section><section powered-by="gulangu"><section><section><section powered-by="gulangu"><section><section><p>欢</p></section></section></section></section><section><section powered-by="gulangu"><section><section><p>迎</p></section></section></section></section><section><section powered-by="gulangu"><section><section><p>关</p></section></section></section></section><section><section powered-by="gulangu"><section><section><p>注</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 powered-by="gulangu"><section><p><img src="image/20201019/fab8ebcd13dd09a7eba2486fa1ca4eb6_7.jpg" /></p></section></section></section><section><section powered-by="gulangu"><section><section></section></section></section></section><section><section powered-by="gulangu"><section><section><p>关注我们</p><p>一起涨姿势！</p></section></section></section></section></section></section></section>