Departamento de Biologia Molecular, São José do Rio Preto, SP, Brasil.
Braz J Med Biol Res. 2010 Dec;43(12):1160-6. doi: 10.1590/s0100-879x2010007500128. Epub 2010 Nov 19.
The main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. The system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. We developed a software tool to reconstruct the target's three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. We present details on the hardware and software implementation. We imaged phantoms and heart and kidneys of rats. When using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. In this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. Appropriate sensitivity to study the target of interest was attained in both cases. Additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. In conclusion, a high resolution single photon emission computed tomography (SPECT) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. This type of system has important implications for research areas such as Cardiology, Neurology or Oncology.
本研究的主要目的是升级一台临床γ相机，以获取小动物器官的高分辨率断层图像。该系统基于一台临床γ相机，我们为其适配了一个专用的小孔准直器和一个基于计算机控制步进电机的目标定位和旋转装置。我们开发了一个软件工具，基于最大似然算法，从一组平面投影重建目标的发射三维分布。我们介绍了硬件和软件实现的详细信息。我们对体模和大鼠的心脏和肾脏进行了成像。使用小孔准直器时，成像系统的空间分辨率和灵敏度取决于探测器与准直器之间以及探测器与目标之间的距离和小孔直径等参数。在本研究中，当使用 1.5 和 1.0 毫米直径的小孔时，我们达到了 0.6 毫米的目标体素尺寸和优于 2.4 和 1.7 毫米的全宽半最大值的空间分辨率。在两种情况下，都获得了对感兴趣目标的适当灵敏度。此外，我们还表明，仅使用 12 个投影就足以获得高质量的重建结果，这一结果意味着采集时间显著减少，并为放射性示踪剂动态研究提供了可能性。总之，使用商用临床γ相机开发了一种高分辨率单光子发射计算机断层成像（SPECT）系统，可获取小动物器官的详细容积图像。这种类型的系统在心脏病学、神经病学或肿瘤学等研究领域具有重要意义。
