SCINTILLATION CAMERA WITH MULTICHANNEL COLLIMATORS.
SCINTILLATION CAMERA WITH MULTICHANNEL COLLIMATORS.
复制标题
带有多通道准直器的闪烁相机。
作者：
H. Anger
闪烁相机是一种灵敏的电子仪器，用于拍摄伽马射线和发射正电子的同位素在体内的分布。这些图像与从机械扫描仪获得的图像相似，但它们的生成时间要短得多。没有使用扫描，因为闪烁相机在整个曝光时间内对其视野的所有部分都很敏感。为了获得活度分布的图像，准直器首先将对象的伽马射线图像投影到闪烁体上。这里描述的仪器使用的是直径11%英寸、厚3英寸的单一碘化钠晶体。通过光学光导耦合到晶体的是由19个倍增光管组成的紧密排列的六角形阵列。光电管可以观察到发光体中的重叠区域，这样每一次闪烁产生的光就会在19个光管之间分配。闪烁体、光导和光电管的组合称为图像探测器(1)。光电管连接到一台模拟计算机，该计算机识别晶体中发生的每一次闪烁的X和Y坐标以及亮度。所有的光峰闪烁在示波器上被复制为点闪光，其相对位置与闪烁体中发生的位置相同。闪光灯在一段时间内被拍摄下来，并产生被摄体的图像。为了获得给定对象和放射性核素的灵敏度和分辨率的最佳组合，应使用最佳准直方法。简要介绍了针孔、多通道和正电子符合三种准直方法(2)。对于正电子发射体，重合准直对于大对象和小对象都具有极好的灵敏度和分辨率。对于包含伽马射线发射器的小对象，针孔准直是选择的方法。它被用来获得甲状腺等小对象的高分辨率照片。然而，对于大型伽马射线发射对象，如大脑或肝脏，具有大量平行孔(2-9个)的准直器提供了最佳的灵敏度和分辨率组合。图1中显示了带有闪烁相机图像探测器的这种类型的准直器的示意图。
The scintillation camera is a sensitive electronic instrument for taking pie tures of the distribution of gamma-ray and positron-emitting isotopes in vivo. The pictures are similar to those obtained from mechanical scanners, but they are produced in much less time. No scanning is employed because the scintillation camera is sensitive to all parts of its field of view during the entire exposure time. To obtain an image of activity distribution a collimator first projects a gamma-ray image of the subject onto a scintillator. The instrument described here uses a single sodium iodide crystal 11% inches in diameter by 3@inch thick. Coupled to the crystal through an optical light guide is a close-packed hexagonal array of 19 multiplier phototubes. The phototubes view overlapping areas in the seintillator so that light from each scintillation divides among the 19 tubes. The combination of scintillator, light guide, and phototubes is called an image detector (1). The phototubes are connected to an analog computer that identi fies the X and Y coordinates and the brightness of each scintillation occurring in the crystal. All photopeak scintillations are reproduced on an oscilloscope as point flashes of light in the same relative positions in which they occurred in the scintillator. The flashes are photographed over a period of time, and an image of the subject results. To obtain the best combination of sensitivity and resolution for a given subject and radionuclide, the optimum collimation method should be used. A brief account of the three collimating methods—pinhole, multichannel, and positron coincidence—has been given (2). For positron emitters, coincidence collimation gives excellent sensitivity and resolution for both large and small subjects. For small subjects containing gamma-ray emitters, pinhole collimation is the method of choice. It is used to obtain high-resolution pictures of small subjects such as the thyroid gland. However, for large gamma-ray emitting subjects, such as the brain or liver, collimators with large numbers of parallel holes (2-9) give the best com bination of sensitivity and resolution. A drawing of this type of collimator is shown with the scintillation camera image detector in Figure 1.