Detective quantum efficiency of a phosphor-coupled photodiode array detector for use in digital X-ray tomosynthesis systems.

The X-ray imaging performance of a phosphor-coupled photodiode array detector was assessed for use in a cone-beam computed tomography (CBCT) system for printed-circuit board inspection. The radiographic image quality of a detector is mainly responsible for the tomographic image quality. The radiographic image quality can be improved by increasing the X-ray exposure level, but CT scans at higher exposure can impose an enormous heat load on the X-ray tube. In this study, the detective quantum efficiency (DQE) was used to describe the image quality per air kerma as a metric to assess the detector performance. Measurement results were obtained for 40-kVp and 50-kVp tungsten-target X-ray beams, which show that the DQE of the detector is tolerant of air kerma levels as low as 0.8 μ Gy. Below this level, the electronic noise of the detector system could degrade the DQE performance. The concept of DQE and the measurement procedure are described, including the modulation-transfer function and the noise-power spectrum. [ABSTRACT FROM AUTHOR]