Morton E J, Swindell W, Lewis D G, Evans P M
Joint Department of Physics, Institute of Cancer Research, Sutton, Surrey, England.
Med Phys. 1991 Jul-Aug;18(4):681-91. doi: 10.1118/1.596661.
An imaging device has been developed to acquire images during external photon-beam radiotherapy treatments. It consists of a linear array of 128 zinc tungstate (ZnWO4) scintillation crystals each of which is individually optically coupled to a photodiode and associated electronics. The image is formed by scanning the linear array across the radiation field using a stepping motor under the control of a microcomputer. Image archive, display, and analysis are performed using a microVAX II computer. Results from a general theoretical analysis are presented before a detailed description of the particular detector construction. The mechanical design of the detector is such that the detector is automatically positioned to within a millimeter relative to the treatment source. This simplifies procedures for analyzing setup variations when comparing a treatment image to any other treatment, or planning, images. Image acquisition takes under 4 s with a contrast resolution of better than 1% at a spatial resolution of 2.5 mm in the object plane. The primary dose used to form these images is 0.55 cGy although the dose received by the patient will be closer to 25 cGy due to the linear scanning geometry and 3.8-s scan time that is used.
已开发出一种成像设备，用于在外部光子束放射治疗期间采集图像。它由128个钨酸锌（ZnWO4）闪烁晶体的线性阵列组成，每个晶体都单独与一个光电二极管及相关电子设备进行光学耦合。通过在微型计算机的控制下使用步进电机使线性阵列在辐射野上扫描来形成图像。使用微型VAX II计算机进行图像存档、显示和分析。在详细描述特定探测器结构之前，先给出一般理论分析的结果。探测器的机械设计使得探测器能够自动定位到相对于治疗源在一毫米范围内。这简化了在将治疗图像与任何其他治疗或计划图像进行比较时分析设置变化的程序。图像采集时间不到4秒，在物平面上空间分辨率为2.5毫米时，对比度分辨率优于1%。用于形成这些图像的主要剂量为0.55厘戈瑞，不过由于采用线性扫描几何结构和3.8秒的扫描时间，患者接受的剂量将更接近25厘戈瑞。
