We are very grateful for the financial support of the Physics Department of CINVESTAV. We also want to thank our technician Marcos Fontaine Sanchez for his remarkable assistance with the set up. Thanks a lot to Sarah LaPointe for reviewing the English-language of this document.

1.制备PET的安装程序<ol><li>准备PMT的加上塑料闪烁体片。根据其种类的PMT（大小，光电阴极的形状）的建立一个适当的闪烁体片，以适应与PMT的光电阴极。 <ol><li>裹闪烁体块用黑色胶带。离开一侧揭露的，因为它会被加上的PMT光入射。 注:重要的是，这些作品都是以前抛光，以避免光积累的损失。 </li></ol></li><li>清洁的PMT光入射与醇（70％的商业酒精浓度）然后应用光学润滑脂它和闪烁体的未覆盖的面。加上光电倍增管面的闪烁体，并与更多的黑色胶带包装他们。 <ol><li>光电倍增管连接到源电压（一个电缆被包括为每个PMT，在这种情况下，偏压14V的偏压和0.5伏电压控制）。识别通过连接从PMT的信号来PMT信号电缆连接到一个标准数字示波器通道（一个信号电缆还包括用于每一个光电倍增管）。转弯时的开/关在实验室中的光观察的变化的信号的振幅，以验证不存在光损失。重复每个四个探测器，在此步骤，其中一个检测器装置，闪烁体加的PMT。 </li></ol></li><li>通过将一个检测器的闪烁器部分上面另一个检测器的相应部分建立一个巧合系统。把所谓的鉴别和逻辑单元模块两个NIM（核仪器模块）仪器在NIM箱子。 </li><li>连接从检测器的输出信号到一个鉴别器模块的输入端。段中的与模式使用一个逻辑单元中，通过选择这样的逻辑的情况下，在逻辑单元的前面板。连接两个鉴别器输出的逻辑单元输入。 注:和的是，选择当两个平方信号到达同一时间或在重合的逻辑运算。 </li><li>有限公司nnect在定标器模块中的逻辑单元的输出信号（此信号计数数字信号）来计算的事件（由宇宙射线击中巧合两个探测器创建）。 </li></ol> 2.获取与PET信号<ol><li>将两个探测器在之前定义的方形区域的对角，所以他们面对对方，20厘米外，并做同样的练习为1.4和1.5，但是这一次，而不是使用宇宙射线（宇宙射线担任临时天然放射源），使用的Na-22辐射源。 <ol><li>将放射源在两个探测器之间的中距离，并通过了定标器模块进行数据采集。系统设置和用于获得巧合的逻辑块的概略结构可在图1，2和 3中看到 。 </li></ol></li><li>通过连接两个判别PMT的输出和测量到达信号的时间差符合输出在示波器。每三个信号的进入示波器输入;将有三个方波信号的示波器屏幕。与水平刻度（时间刻度）测量两个判别信号的时间差。 注意:当放射源是直接在两个检测器之间的中间会有很少或正方形之间没有分离或时间差鉴别信号的平均值，并且当放射性源离开该中心，并靠近一个PMT的再将有平均时间差。 </li><li>发送这些定时信号提供给八个通道的CAMAC（计算机测量和控制）的TDC（时间 - 数字转换器）模块中的一个。要做到这一点，连接的逻辑与贸发局的输入输出所谓的"开始"，然后连接探测器区分输出到TDC输入这是所谓的"STOP"。该和信号必须通过延迟冒顿被推迟乐在为了某些纳秒这个信号，另外两个STOP信号之前到达（ 见图 4）。 </li><li>校准TDC计数单位之间的时间通过一个软件程序，显示示波器（详见第3步）。通过使用放射性源和探测器中的一个之间的距离间隔，测量每个位置的平均时间差（步骤2.3）这样做校准。通过标准总线GPIB（通用仪器总线）这样做标定，建立不同的模块和计算机之间的软件通信。 </li></ol> 3.构建虚拟仪器接口<ol><li>下载并使用LabVIEW软件或任何类似的软件。 注意:要使用LabVIEW工作，就必须有"G编程语言"的一些知识。在这种语言中，没有代码已被写入，所有执行的操作可以从一个软件工具苍白来完成TTE。一个简单的指南与实际的例子可以在工具的帮助中找到。 </li><li>选择前面板工具选项板阵列实用程序（程序变量容器）来保存TDC输出数据。 注意:"前面板"是虚拟仪器给用户和"框图"的图形接口用于软件编程。 </li><li>绘制数据采集（从上止点时的数据），通过选择地块菜单逻辑工具。找出与该源的每个位置相关的情节数据。由一些厘米，从不同的探测器行源距离执行此操作。 </li><li>取使用统计函数（平均值）从数学菜单工具的数据的平均值，并选择集中在平均值的间隔。然后，根据该编程逻辑随后，使用从阵列菜单必要的工具以删除所有的数据与该间隔之外的值。 </li><li>从日选择指标Ë框图工具板，以显示存储的每个阵列中的数据的数目，并确定一些容器具有最大数目的存储数据。 </li><li>获取数据的平均值在3.5步选择的每个阵列中，并利用这些信息建立了一整套的时间间隔值，使用该LabVIEW程序框图工具选项板中的每个源位置。 </li><li>选择的指标从面板工具调色板一个数组来存储在步骤3.6的测量值的序列中得到的平均值。 </li><li>从框图工具选项板的情况下的结构关系每个位置，其步骤3.7各区间，每个区间关联到一个虚拟的前面板工具面板的LED阵列。 </li><li>注意，每个信号取到达到TDC信道的时间:当放射源从中间移近一个检测器，观察LED的编程阵列（ 参见图5中的虚拟源的移动</stro纳克&gt;）向右移动在计算机中。 </li><li>包括前面板工具选项板的总时间采集控制（可变编程元素）。 注:所述定位的效率将取决于这个控制时间工具:越时间采集需要时，更精确地模拟放射源的虚拟对象将给出正确的位置。 </li></ol> 4.图形结果<ol><li>为了校准的目的，将源在任何中间位置相对于耦合对检测器中的一个。进行测量30分钟，并与数据获取的，采取累计每2分钟的值的平均值。重复此过程，对于不同的源位置和绘制在所有位置从每个检测器的平均值（ 参见图6和7）。的探测器值的差异绘制在图8。 </li><li>为了获得更好的地区环境部门一道LTS，选择两个检测器具有类似的数据值，形成一对夫妇。为了测试这一点，把PMT的控制电压到其较低的值，在这种情况下，为0.5V开始由检测器输出连接到定标器输入测量用一个固定的时间定标器模块检测到的事件的数量。增加0.01伏电压，再次测量。重复此过程，以达到最大可能的控制值，在这种情况下，0.9V。 <ol><li>绘制检测到的事件与半对数刻度的控制电压的值 （见图9）。夫妇有相似的分布探测器对。 </li></ol></li><li>为了测试该系统的灵敏度，将在沿行一些等间距的中间位置的放射性源，在这种情况下有五个。采集数据5分钟，在每一个位置上，并独立地绘制的每个检测器获得的值的平均值和中值（见图10和11）。 </li></ol>

<ol>
	<li>Cerello, P., Pennazio, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+innovative+detector+concept+for+hybrid+4D-PET/MRI.">An innovative detector concept for hybrid 4D-PET/MRI.</a> Imaging. Nucl. Instr. Meth. Phys. Res. 702, 1-3 (2013).</li><li>Muehllerher, G., Karp, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Positron+tomography+emission.">Positron tomography emission.</a> Phys. Med. Biol. 51, R117-R137 (2006).</li><li>Conti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State+of+the+art+and+challenges+of+time+of+flight+PET.">State of the art and challenges of time of flight PET.</a> Physica Medica. 25 (1), 1-11 (2008).</li><li>Abreu, Y., Pi&#241;era, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simulation+of+a+PET+system+and+study+of+some+geometry+parameters.">Simulation of a PET system and study of some geometry parameters.</a> AIP conference. 1032, 219-221 (2008).</li><li>Langner, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Development of a parallel Computing optimized head movement correction method in PET. , (2003).</li><li>Budinger, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-of-flight+PET.">Time-of-flight PET.</a> J. Nucl Med. 28 (3), 73-78 (1983).</li><li>Leo, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Techniques for Nuclear and Particle Physics Experiments. , (1987).</li><li>Budinger, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instrumentation+trends+in+nuclear+medicine.">Instrumentation trends in nuclear medicine.</a> Semin Nucl Med. 7 (4), 285-297 (1977).</li><li>Burnham, C., Bradshaw, J., Kaufmann, D., Chesler, D., Browner, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Positron+tomography+employing+a+one+dimension+BGO+scintillation+camera.">A Positron tomography employing a one dimension BGO scintillation camera.</a> IEEE Trans. Nucl. Sci. 30 (1), 661-664 (1983).</li><li>Burnham, C., Bradshaw, J., Kaufmann, D., Chesler, D., Steams, C. W., Browner, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+of+a+cylindrical+shape+scintillation+camera+for+positron+tomographs.">Design of a cylindrical shape scintillation camera for positron tomographs.</a> IEEE Trans. Nucl. Sci. 32 (1), 889-893 (1985).</li></ol>

There are no competing financial interests.

该系统的一个重要方面是有很好的控制了空间和时间分辨率。 PET的空间分辨率由放射性衰变和湮灭，的物理特性，而且还通过一致登记的技术方面（步骤1.1和1.2）和由错误，如对象的运动的外部源的检查5中限定。因此，测量的确切位置将取决于飞行时间差（步骤2.4）。一种技术实现了良好的时间分辨率测量TOF 6的分布的半峰全宽（FWHM）。 每个PMT的特点是获得它的曲线被称为"高原"7,8。这条曲线代表由PMT与处于半对数标度的控制电压检测到的事件的数量。最平坦部分对应的极大的稳定性的区域（ 参见图9）。另一个特点采取INTØ帐户的电压值，在这个高原地带的稳定性。在这种情况下0.82五获得作为控制电压（步骤4.2）。 选择每对检测器的简单试验包括在评估在不同的位置上的效率的造之间的中间位置的数目。源被放置在检测器之间的不同位置，和数据取为5分钟（参见图 10和11）。对于此测试，5个位置被选定;行有20个厘米经度，所以每个位置是在2，6，10，14和18厘米相对于一个光电倍增管。 从以前的测试中，从每个TDC测量的震级进行了评价。作为第一选择，它从这个幅度利德远的所有数据被丢弃，并且计算平均值。另一种选择是通过考虑周围之前计算的平均数据的时间间隔进行，而该区间之外的数据是DISCArded。以这种方式，噪声信号受到控制。 值得说只有2分钟，需要找到具有优良的效率（见结果）的放射源。然而，当时间缩短为2至1分钟或甚至30秒，定位源的效率减小。此刻，该PET系统由四个探测器，但也可以增加检测器的数量，以提高效率和空间分辨率。然而，这台样机，这项工作的主要目的是满足9，10。 这样做的主要优点设立是它内建如高能物理共同致力于仪器在一些地区任何实验室的电子设备。当其中一些设备已经出现在实验室里是不是太困难或昂贵的完成整个实验装置。由于这是前面提到的，这个宠物系统的教授和学生有POssibility理解定位在空间中的放射性源，这是基本的PET工作特性的基本属性。在将来，人们可以提高许多这种系统的不同的元素，并把它应用，不仅为学术也为研究目的。

正电子发射断层摄影术是用于获得主体的内组织和器官的数字图像的非侵入性成像技术。各种非侵入性技术存在允许之一在患者的内部工作如计算机轴向断层（TAC）和磁共振成像（MRI）获得的图像和信息。既提供良好的空间分辨率，并另外用于在解剖和生理的研究应用。尽管相对的PET得到较少的空间分辨率，它提供了关于在感兴趣的区域中发生的代谢的更多信息。的PET被广泛用于获得功能和形态学的信息;其主要临床应用是在肿瘤学，神经病学和心脏病学领域中。此外，PET图像可以帮助医生更好地诊断， 例如，建立肿瘤治疗计划。 PET系统的基本工作原理是两坡的检测吨或伽玛射线从一个正电子 - 电子湮灭对到来，既飞行在朝向检测器，它通常由结合光电倍增管的闪烁体晶体的方向相反。闪烁体结晶转变的γ辐射转化为可见光，行进到的PMT经由一个光电过程的光信号转换为电脉冲。内的光电倍增管的电子设备称为倍增电极都存在，把它发送到一个读出系统之前这增加了电荷的幅度。创建这两个探测光子当一个正电子（电子带正电）由同位素流体，将其注入体内的血流中发射的，歼与体内的电子。读出系统测量重合两回到后端的光子相对于时间基准并且进一步它衬底既次，得到的差的到达时间。该系统使用这个时间差来计算空间中的位置WHERE辐射源发射两个光子，并且因此电子对湮灭发生的位置。 的PET系统中的某些功能，必须定义来优化图象的质量和增加的空间和时间分辨率。要考虑的一个特点是响应的线（LOR），定义为两个光子的湮灭过程之后行驶的距离。另一个特点要考虑的是飞行（TOF）的时间。图像质量还取决于外部特征，主要是身体器官和疗程1期间患者的动作。在PET系统中使用的同位素是称为贝塔+发射器。这些同位素具有短半衰期（秒数量级上）。他们生产的颗粒加速器（回旋加速器）时有稳定的元素轰炸质子或氘核引起核反应。这种反应变换稳定的元素融入到不稳定的同位素，如C-11，N-13，O-15，F-18等等2。 有两种类型的PET。 （1）常规:此使用飞行时间信息只以识别沿其湮没发生线，但它是无法确定两个光子的原点处。它需要额外的分析或迭代重建算法来估计这一点。 （2）TOF PET:利用TOF差来定位所发射的正电子的湮灭位置。时间分辨率被用在重建算法作为内核对于一个本地化概率函数3。 我们的主要目的是要证明的PET，其用于定位在空间中的辐射源的主要功能。这里提出的PET系统组的主要范围是提供一种基本的PET结构导向为学术公众，并解释，在一个简单的方法，它的主要性能。

<table border="0" cellpadding="0" cellspacing="0" width="675">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:237px;">Low threshold Discriminator</td>
			<td style="width:152px;">CAEN</td>
			<td style="width:119px;">N845</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Logic Units</td>
			<td>Lecroy</td>
			<td>365AL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Time delay</td>
			<td>CAEN</td>
			<td>N108A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oscilloscope</td>
			<td>Tektronic</td>
			<td>TDS3014C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Quad Scaler and preset counter</td>
			<td>CAEN</td>
			<td>N1145</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TDC</td>
			<td>Lecroy</td>
			<td>2228</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PMT&#8217;s</td>
			<td>Hamamatsu</td>
			<td>H5783p</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power Chasis</td>
			<td style="width:152px;">Lecroy</td>
			<td style="width:119px;">1403</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">GPIB Interface</td>
			<td style="width:152px;">Lecroy</td>
			<td style="width:119px;">8901A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NIM Power Supply</td>
			<td style="width:152px;">Lecroy</td>
			<td style="width:119px;">1002B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CAMAC Crate</td>
			<td style="width:152px;">Borer-co</td>
			<td style="width:119px;">1902A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scintillator Crystals</td>
			<td>Bicron</td>
			<td>408</td>
			<td>1cm x 2cm x 5cm&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power Supply</td>
			<td>Agilent</td>
			<td>E3631</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Na 22 Radioactive Source</td>
			<td style="width:152px;"></td>
			<td style="width:119px;"></td>
			<td>activiti 2&#956;Ci</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Software LabView 7.1</td>
			<td>National intruments</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">lemo cables connectors</td>
			<td style="width:152px;"></td>
			<td style="width:119px;"></td>
			<td>2ns, 3ns and 8ns</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">isolator film</td>
			<td style="width:152px;"></td>
			<td style="width:119px;"></td>
			<td></td>
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a basic positron emission tomography system constructed to locate a radioactive source in a bi-dimensional space

一个简单的正电子发射断层扫描（PET）样机已经建成全面检定其基本工作原理。在PET样机，通过偶合塑料闪烁体晶体光电倍增管或光电倍增管的其中被放置在相对的位置​​，以检测从一个放射源，其中被放置在PET的几何中心喷射2伽马射线创建设置。所述原型包括四个探测器在一个20厘米直径的圆几何放置，并在该中心放射源。通过从中间移动放射源厘米的系统中的一个是能够​​通过测量任何两个PMT的飞行之间的差异的时间，以检测的位移，并与该信息，系统可以计算在图形界面的虚拟位置。以这种方式，所述原型再现的PET系统的主要原则。它能够确定在2行的代以4cm间隔源的实际位置tection服用不到2分钟。

两个主要结果与该PET系统来实现。第一:虚拟放射源的视觉效果之间的一个有效的同步移动时的实际放射性样品。与此方案，用户可以控制的采集时间，重复在同一位置的数目，围绕采集数据的意思是，在其他的时间间隔的变化。第二:同时逻辑的结构简单的结构，以获得时间差的两个信号之间，转换这个时间差为距离来计算源的最终位置。 在一个检测线，它足以只使用一个逻辑模块"和"，以鉴别从巧合或外部噪声传来的信号。在这种情况下，存在其中两个要求其逻辑模块的两个检测线。如果检测器的数量增加，它是必要的，包括另一个检测线并且还包括"或"模块（ 见图 3）。 另一个特征，考虑到是与TOF PET系统，并且在所有位置的每5分钟的现有的PET系统之间的比较;图6 和 7示出测量为不同位置的几个检测器的系统的响应。对于源的每个位置，有TDC响应的曲线。对于每一组测量，线性特性的预期，并且允许一个之间建立的位置和时间的关系。即使有变动或重叠，存在一个稳定性的改善，只要采集时间增加而增加。 图 10和11示出的优点时服用，积累的数据平均的差，以获得更好的校准的<html>系统。用平均，结果变得更加稳定，和的TDC单位增加给虚拟放射源的一个更好的定位的分离。我们的最终结果是通过重复在2分钟内30次测量得到。为了区分两行采集，他们被称为ij和EF线。对于此次收购线IJ，大约90％的平均效率被发现，同时行EF 87％左右达到。为整个系统，所得到的效率为85％左右。 <img alt="图1" src="/files/ftp_upload/52272/52272fig1.jpg" /> 图1.光电倍增管的排列，显示的二维设置了4个光电倍增管。每个PMT的位置从几何中心10厘米。在图像的中心，所述的Na-22放射性同位素产生一对背到背光子。通过检测这些光子在一致时，放射性源可位于。72 / 52272fig1large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图2" src="/files/ftp_upload/52272/52272fig2.jpg" /> 用于获得放射性源的信号位置，其中包括鉴别图2检测系统。NIM模块，延迟模块，和逻辑单元。下面这些谎言一CAMAC机箱与贸发局和GPIB控制模块。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/52272/52272fig3.jpg" /> 图3的逻辑块中。在这个方案中的光电倍增管4被示出，命名为I，J，e和f，连接到四个&#39;或&#39;连接到一个共同的&#39;与&#39;模块的模块。操作很简单:当一个信号为s耳鼻喉科由一个光电倍增管，3的"或"模块发送的信号，但这是不够的，"与"模块的操作要求，只有当多个PMT发送一个信号时（ 即，有巧合）。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图4" src="/files/ftp_upload/52272/52272fig4.jpg" /> 图4.系统方案，在右上角的放射性同位素被放置在光电倍增管，其将信号发送到它转换来自信号从模拟到数字脉冲鉴别器之间。脉冲然后通过逻辑块通过。相同的信号被发送到延迟模块，以便测量的时间差。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig4large.jpg" target="_blank">请点击查看</a>一个更大的版本这个数字。 <img alt="图5" src="/files/ftp_upload/52272/52272fig5.jpg" /> 图5. 软件接口，包括LED阵列，模拟放射源的位置，当程序完成收购，一个LED接通指示信号源的位置。在图像的顶部还有其他类型的LED的代表发射线。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig5large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图6" src="/files/ftp_upload/52272/52272fig6.jpg" /> 图6.校准使用PMT称为岛 ​​连续测量进行与累积的数据取平均值。每次测量持续了2分钟。每种颜色corresp哔声的检测器之间的各个位置上。一段时间后，得到一个明确的信号分离，这意味着源的立场是众所周知的。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig6large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图7" src="/files/ftp_upload/52272/52272fig7.jpg" /> 图7.校准使用PMT称J。该图与前一个显示第j PMT的平均值。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig7large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图8" src="/files/ftp_upload/52272/52272fig8.jpg" /> 图8.校准使用累积数据平均值之间的差。每个颜色对应一个断定离子的检测线。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig8large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图9" src="/files/ftp_upload/52272/52272fig9.jpg" /> 图9.高原曲线。在该图中的"平稳"曲线对于不同的光电倍增管被示出。这里的控制电压而变化从0.5到0.9伏。曲线开始弯曲约0.6伏;有些陡峭的曲线，对应更高的稳定性;在另一方面，一些曲线如橙子线的数值达到更高值。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig9large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图10" src="/files/ftp_upload/52272/52272fig10.jpg" /> 图10.耦合反应的.h示ERE从光电倍增管e和f，放置在沿着检测线的五个不同地点放射源位置的平均值和中值的幅度。所获得的统计数据使用在5分钟所获得的数据。该曲线应尽可能垂直。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig10large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图11" src="/files/ftp_upload/52272/52272fig11.jpg" /> 图11.耦合响应。这里的模拟信息，但现在对i和j示出了第二对光电倍增管。相对水平线被观察到，这意味着以前的PMT对是更好的，在空间分辨率方面。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52272/52272fig11large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space at JoVE.com

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space

We present a simple but well-constructed Positron Emission Tomography (PET) system and elucidate its basic working principles. The goal of this protocol is to guide the user in constructing and testing a simple PET system.

一个基本的正电子发射断层扫描系统构建以定位放射源的双维空间

A simple Positron Emission Tomography (PET) prototype has been constructed to fully characterize its basic working principles. The PET prototype was ...

a-basic-positron-emission-tomography-system-constructed-to-locate

Nanyang Technological University

Research

JoVE Journal

Engineering

8.5K 次观看.  Centro de Investigacion y de Estudios Avanzados del IPN (Cinvestav). We present a simple but well-constructed Positron Emission Tomography (PET) system and elucidate its basic working principles. The goal of this protocol is to guide the user in constructing and testing a simple PET system.

视频: A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

使用中子自旋回声解决放牧发生率散射调查有机太阳能电池材料

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

科研

工程学

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

火焰在实验的先进光源:全新洞察烟灰形成过程

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction.
Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of &gt; 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm.
Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed.

The use of energy dispersive X-ray tomography in the scanning transmission electron microscope to characterize elemental distributions within single nanoparticles in three dimensions is described.

能量色散X射线断层摄影术对个人纳米3D元素映射

Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

检测和钯的回收，从城市矿山黄金和钴金属使用标有纳米货车车轮形的孔隙新型传感器/吸附剂

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an elastomeric dielectric membrane sandwiched between two compliant electrodes. The large actuation strains of these transducers when used as actuators (over 300% area strain) and their soft and compliant nature has been exploited for a wide range of applications, including electrically tunable optics, haptic feedback devices, wave-energy harvesting, deformable cell-culture devices, compliant grippers, and propulsion of a bio-inspired fish-like airship. In most cases, DETs are made with a commercial proprietary acrylic elastomer and with hand-applied electrodes of carbon powder or carbon grease. This combination leads to non-reproducible and slow actuators exhibiting viscoelastic creep and a short lifetime. We present here a complete process flow for the reproducible fabrication of DETs based on thin elastomeric silicone films, including casting of thin silicone membranes, membrane release and prestretching, patterning of robust compliant electrodes, assembly and testing. The membranes are cast on flexible polyethylene terephthalate (PET) substrates coated with a water-soluble sacrificial layer for ease of release. The electrodes consist of carbon black particles dispersed into a silicone matrix and patterned using a stamping technique, which leads to precisely-defined compliant electrodes that present a high adhesion to the dielectric membrane on which they are applied.

This manuscript shows the fabrication process for the manufacture of dielectric elastomer soft actuators based on silicone membranes. The three key stages of production are presented in detail: blade casting of thin silicone membranes; pad printing of compliant electrodes; and the assembly of all the components.

有机硅为基础的介电弹性体致动器的制作工艺

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data acquisition times with high spatial resolution. In the electronics industry there is serious interest in performing failure analysis on 3D microelectronic packages, many which contain multiple levels of high-density interconnections. Often in tomography there is a trade-off between image resolution and the volume of a sample that can be imaged. This inverse relationship limits the usefulness of conventional computed tomography (CT) systems since a microelectronic package is often large in cross sectional area 100-3,600 mm2, but has important features on the micron scale. The micro-tomography beamline at the Advanced Light Source (ALS), in Berkeley, CA USA, has a setup which is adaptable and can be tailored to a sample&#39;s properties, i.e., density, thickness, etc., with a maximum allowable cross-section of 36 x 36 mm. This setup also has the option of being either monochromatic in the energy range ~7-43 keV or operating with maximum flux in white light mode using a polychromatic beam. Presented here are details of the experimental steps taken to image an entire 16 x 16 mm system within a package, in order to obtain 3D images of the system with a spatial resolution of 8.7 &#181;m all within a scan time of less than 3 min. Also shown are results from packages scanned in different orientations and a sectioned package for higher resolution imaging. In contrast a conventional CT system would take hours to record data with potentially poorer resolution. Indeed, the ratio of field-of-view to throughput time is much higher when using the synchrotron radiation tomography setup. The description below of the experimental setup can be implemented and adapted for use with many other multi-materials.

For this study synchrotron radiation micro-tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron&#39;s high flux and brightness the sample was imaged in just 3 min&#160;with an 8.7 &#181;m spatial resolution.

利用同步辐射微断层调查的多尺度三维微电子封装

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

A System to Create Stable Nanoparticle Aerosols from Nanopowders

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring minimal amounts of test materials (min. 200 mg), for studying powder aerosolization behavior and aerosol properties. The aerosolization procedure follows the concept of the fluidized-bed process, but occurs in the modified volume of a V-shaped aerosol generator. The airborne particle number concentration is adjustable by controlling the air flow rate. The system supplied stable aerosol generation rates and particle size distributions over long periods (0.5-2 hr and possibly longer), which are important, for example, to study aerosol behavior, but also for toxicological studies. Strict adherence to the operating procedures during the aerosolization experiments ensures the generation of reproducible test results. The critical steps in the standard protocol are the preparation of the material and setup, and the aerosolization operations themselves. The system can be used for experiments requiring stable aerosol concentrations and may also be an alternative method for testing dustiness. The controlled aerosolization made possible with this setup occurs using energy inputs (may be characterized by aerosolization air velocity) that are within the ranges commonly found in occupational environments where nanomaterial powders are handled. This setup and its operating protocol are thus helpful for human exposure and risk assessment.

We designed and developed an effective nanopowder aerosolization setup and operating protocol. The system generated nanoparticle aerosols with stable number concentrations and size distributions for long durations, requiring only small quantities of test material (min. 200 mg).

系统创建从纳米粉体纳米稳定气溶胶

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring ...

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Silicon photonic chips have the potential to realize complex integrated quantum systems. Presented here is a method for preparing and testing a silicon photonic chip for quantum measurements.

量子干涉效应在硅谐振环光子源测量

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit ...

Plasmonic Trapping and Release of Nanoparticles in a Monitoring Environment

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few can observe immobilized particles. Moreover, a limited number of studies have experimentally measured the exertable forces on the particles. The designs can be classified as the protruding nanodisk type or the suppressed nanohole type. For the latter, microscopic observation is extremely challenging. In this paper, a new plasmonic tweezer system is introduced to monitor particles, both in directions parallel and orthogonal to the symmetric axis of a plasmonic nanohole structure. This feature enables us to observe the movement of each particle near the rim of the nanohole. Furthermore, we can quantitatively estimate the maximal trapping forces using a new fluidic channel.

A microchip fabrication process that incorporates plasmonic tweezers is presented here. The microchip enables the imaging of a trapped particle to measure maximal trapping forces.

电浆捕获和纳米粒子的释放在监控环境

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

记录实验室闪电弧宽带高分辨率发射光谱的方法

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...