title: Patient exposure requirements for high contrast resolution in digital radiographic systems.
abstract: The contrast resolution of modern digital radiographic equipment is primarily limited by quantum mottle. The derivation of the contrast resolution of a system as a function of radiation exposure is presented. Calculations based on this derivation show that achieving 0.8% contrast resolution (128 meaningful gray levels) with 1-mm spatial resolution may require a patient exposure of 1.7 rad (1.7 cGy) per image of a thick body part (20 cm tissue). Acceptable clinical studies often can be obtained with only 5% contrast resolution (20 meaningful shades of gray), but even this level of contrast may require a patient exposure of nearly 90 mrad (0.9 mGy) per image. A comparison of three commonly used methods of reducing patient radiation exposure (pulsed imaging, temporal averaging, and recursive filtering) shows that, in theory, a pulsed system achieves the highest contrast resolution for the same total exposure.
mesh_terms: D003201:Computers; D006801:Humans; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement; D013679:Technology, Radiologic