Physical evaluation of a system for direct digital intra-oral radiography based on a charge-coupled device

Objectives: To determine technical properties of a direct digital intra-ora l radiographic system, the Dixel(R)(J Morita Corporation, Kyoto, Japan). Methods: A dose response function and the dark current were calculated from two series of exposures to a homogeneous radiation field. The line spread function (LSF) and the modulation transfer function (MTF) were determined f rom radiographs of an edge. The noise power spectrum (NPS) was determined a t three exposures from radiographs exposed to homogeneous radiation fields. Noise equivalent quanta (NEQ) were calculated from the one-dimensional NPS and the MTF. The detective quantum efficiency (DQE) was determined from th e NEQ and a representative value of the photon fluence. Signal-to-noise rat ios (SNR) were calculated from the NEQs and different signal contrasts. Results: The dose response function demonstrated a slight curvature. There was no effect of the dark current. NPS ranged from 10(-5)-10(-7) mm(2) depe nding on exposure and frequency. At a peak of about 2 cycles/mm the DQE is on an average about 30 per cent. SNRs are favorable. Conclusion: The technical properties found in this study indicate that the Dixel(R)system is suitable for intra-oral dental radiography.