Physical performance measures of radiographic imaging systems.

New systems and technologies for dental radiographic imaging are being introduced at an increasing rate. Established methods of physical measurement allow the imaging performance of these systems to be quantified. These quantitative measures are important when comparing the imaging performance of competing systems. This review presents an overview of the main concepts in the assessment of the physical performance of imaging systems including signal transfer, as described by both the characteristic curve and modulation transfer function (MTF), and image noise, as described by the Noise Power Spectra. These measures can be combined to produce signal-to-noise ratio descriptors such as Noise Equivalent Quanta and Detective Quantum Efficiency which give an overall description of imaging system performance. Subjective means of measuring image quality, which naturally include the performance of the image display system and the observer, are also considered as a gauge of system performance.