Gosch D, Ratzmer A, Berauer P, Kahn T
Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Leipzig AöR.
Rofo. 2007 Sep;179(9):896-900. doi: 10.1055/s-2007-963389.
The objective of this study was to examine the extent to which the image quality on mobile C-arms can be improved by an innovative exposure rate control system (grid control). In addition, the possible dose reduction in the pulsed fluoroscopy mode using 25 pulses/sec produced by automatic adjustment of the pulse rate through motion detection was to be determined.
As opposed to conventional exposure rate control systems, which use a measuring circle in the center of the field of view, grid control is based on a fine mesh of square cells which are overlaid on the entire fluoroscopic image. The system uses only those cells for exposure control that are covered by the object to be visualized. This is intended to ensure optimally exposed images, regardless of the size, shape and position of the object to be visualized. The system also automatically detects any motion of the object. If a pulse rate of 25 pulses/sec is selected and no changes in the image are observed, the pulse rate used for pulsed fluoroscopy is gradually reduced. This may decrease the radiation exposure. The influence of grid control on image quality was examined using an anthropomorphic phantom. The dose reduction achieved with the help of object detection was determined by evaluating the examination data of 146 patients from 5 different countries.
The image of the static phantom made with grid control was always optimally exposed, regardless of the position of the object to be visualized. The average dose reduction when using 25 pulses/sec resulting from object detection and automatic down-pulsing was 21 %, and the maximum dose reduction was 60 %.
Grid control facilitates C-arm operation, since optimum image exposure can be obtained independently of object positioning. Object detection may lead to a reduction in radiation exposure for the patient and operating staff.
本研究的目的是检验一种创新的曝光率控制系统（格栅控制）能在多大程度上改善移动C形臂的图像质量。此外，还要确定在使用通过运动检测自动调整脉冲率产生的每秒25个脉冲的脉冲透视模式下可能实现的剂量降低情况。
与传统的曝光率控制系统不同，传统系统在视场中心使用一个测量圆，而格栅控制基于覆盖整个透视图像的方形单元的精细网格。该系统仅将被待可视化物体覆盖的那些单元用于曝光控制。这旨在确保无论待可视化物体的大小、形状和位置如何，都能获得最佳曝光的图像。该系统还能自动检测物体的任何运动。如果选择了每秒25个脉冲的脉冲率且未观察到图像变化，则逐渐降低用于脉冲透视的脉冲率。这可能会降低辐射暴露。使用人体模型检查了格栅控制对图像质量的影响。通过评估来自5个不同国家的146名患者的检查数据，确定了借助物体检测实现的剂量降低情况。
使用格栅控制拍摄的静态人体模型图像始终获得最佳曝光，无论待可视化物体的位置如何。由物体检测和自动降脉冲导致使用每秒25个脉冲时的平均剂量降低为21%，最大剂量降低为60%。
格栅控制便于C形臂操作，因为可以独立于物体定位获得最佳图像曝光。物体检测可能会降低患者和操作人员的辐射暴露。
