Digital radiography with a large-area, amorphous-silicon, flat-panel X-ray detector system.

RATIONALE AND OBJECTIVES

To investigate the image quality of a digital radiography system with an amorphous-silicon, large-area, digital flat-panel detector.

METHODS

A flat-panel detector based on a matrix of amorphous silicon was integrated into a projection radiography system. The scintillator consisted of a layer of structured cesium iodide. The active matrix size of 30002 pixels together with a pixel size of 143 microm provided a large image area of 43 x 43 cm2. Basic image quality parameters such as detective quantum efficiency (DQE) and modulation transfer function (MTF) were measured and compared with those obtained with conventional systems.

RESULTS

The measurement of DQE yielded a high value of 70% at zero spatial frequency. At a system dose equivalent to 400 speed, the DQE of the digital system was a factor of two larger than the DQE of a storage phosphor or screen-film system within the entire spatial frequency range between zero and the Nyquist limit of 3.5 line pairs per millimeter. The flat-panel detector furthermore has an MTF that is superior to that in regular screen-film systems and also provides a substantially larger dynamic range.

CONCLUSIONS

This new technology demonstrates its potential to provide equal or superior image quality to conventional screen-film systems and to reduce patient exposure to radiation dose. The advantages of digital radiography systems, based on a flat-panel detector as an instant image display, facilitation of work flow in the radiology department, and digital networking and archiving, are well in sight.