A fast low‐noise line scan x‐ray detector

A fast, low‐noise line scan detector (NIKOS) for digital radiography has been developed. It consists of an input x‐ray phosphor screen that is coupled to a modified Reticon photodiode array by means of fiber optics with incorporated image intensifier. In its current version the detector can be operated with a maximum 500 Hz image acquisition rate for interlaced readout of two lines of 128 pixels each. Using a Gd 2 O 2 S:Tb x‐ray input phosphor, an afterglow of 25% in the first subsequent readout was observed. We also conducted afterglow measurements on several other powder and single‐crystal phosphors and the photodiode array. Using CdWO 4 , the afterglow of the detector is limited by the lag of the photodiode array of 4.5%. By modifying the readout electronics the noise of the photodiode array was reduced to below 1 Graylevel, corresponding to a signal‐to‐noise ratio of 5200. The detective quantum efficiency (DQE) of the detector ranged from 0.18 to 0.4 for typical signal levels. The sensitivity was 10% saturation per 1.9 mR entrance dose. The modular design of the NIKOS detector allows for individual selection of each component to optimize performance for a given application.