| 摘要 |
<p>The invention relates to an X-ray system which includes an X-ray source (2) and an X-ray detector for deriving an image signal. The X-ray detector includes an X-ray matrix sensor (3), such as an FDXD, which includes a matrix of sensor elements. Preferably, the sensor elements are light-sensitive (18) g(a)-Si sensor elements (photodiodes) and the FDXD is provided with a scintillator layer (6) which converts X-rays into light. The sensor elements generate electric charges that are read out in the form of an image signal that represents the X-ray image. The X-ray matrix sensor is provided with an additional array of detection elements which are arranged between the sensor elements and the X-ray source. More specifically, the detection elements are also g(a)-Si light-sensitive photodiodes. The scintillator layer is arranged between the X-ray matrix sensor and the additional array of detector elements. A partly transparent coating (7) is disposed between the additional array of detector elements and the scintillator layer. The number of detector elements of the additional array is far less than the number of sensor elements. The additional array is employed to derive a dose control signal. The dose control signal represents the local X-ray dose received at the individual detector elements. The dose control signal is employed to control the X-ray source. About 5 % of the light from the scintillator is used to form the dose control signal.</p> |
